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    Wyświetlanie 1-67 z 67
    Tytuł:
    Two-Dimensional Analytical Threshold Voltage Modelling of Pseudomorphic $Si_{0.8}Ge_{0.2}$ p-Channel MOSFETs
    Autorzy:
    Ansaripour, G.
    Powiązania:
    https://bibliotekanauki.pl/articles/1492776.pdf
    Data publikacji:
    2011-12
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    73.23.-b
    Opis:
    In this work we present an analytical model of the threshold voltage of SiGe p-channel metal oxide semiconductor field effect transistor based on the solution of the two-dimensional Poisson's equation and the ground state wave function of Fang and Howard, and taking into account the space charge in the channel and its effect on the surface potential. It is seen that the experimental data are well fitted within the experimental error that shows the appropriateness of the implemented model. Also comparing the calculated results to that of the calculated from the available recent reported models indicates a reasonable improvement to them.
    Źródło:
    Acta Physica Polonica A; 2011, 120, 6; 1043-1046
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Many-Channel Landauer-Like Conductance Formula in a Uniform Magnetic Field
    Autorzy:
    Benamira, F.
    Abdellaoui, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/1418271.pdf
    Data publikacji:
    2012-10
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    73.23.-b
    Opis:
    Linear-response theory is combined with the Landauer viewpoint to describe quantitatively transport in a four-lead mesoscopic structure within the presence of a uniform magnetic field. A new multichannel magnetoconductance formula is derived in the case where the magnetic field is perpendicular to the current-flow. The invariance under magnetic reversal test is confirmed.
    Źródło:
    Acta Physica Polonica A; 2012, 122, 4; 721-724
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Mutual Inductance and Selfinductance in Mesoscopic Systems
    Autorzy:
    Zipper, E.
    Dajka, J.
    Szopa, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/2035547.pdf
    Data publikacji:
    2002-09
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    73.23.Ra
    73.23.-b
    Opis:
    The role played by the magnetostatic interaction in mesoscopic multichannel systems is discussed. We show that the interaction of currents from different channels, when taken in the selfconsistent mean field approximation, leads to selfinductance terms in the Hamiltonian producing an internal magnetic flux. Such multichannel systems can exhibit spontaneous flux or flux expulsion. The dependence of these phenomena on the parameters of the system is discussed.
    Źródło:
    Acta Physica Polonica A; 2002, 102, 3; 419-428
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Terahertz Generation and Detection by Plasma Waves in Nanometer Gate High Electron Mobility Transistors
    Autorzy:
    Knap, W.
    Łusakowski, J.
    Teppe, F.
    Dyakonova, N.
    Meziani, Y.
    Powiązania:
    https://bibliotekanauki.pl/articles/2041635.pdf
    Data publikacji:
    2005-01
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    73.21.-b
    73.23.-b
    Opis:
    The high electron mobility transistors can act as a resonator cavity for the plasma waves that can reach THz frequencies for a nanometer size devices. As was predicted by Dyakonov and Shur in 1993, the steady state of the current flow in a gated 2D electron gas can become unstable leading to the emission of an electromagnetic radiation at the plasma wave frequencies. The theory predicted also that the plasma waves can be used for resonant detection of THz electromagnetic radiation. In the present paper we review our recent experiments on THz emission and detection performed on high electron mobility transistors based on different semiconductor structures: InGaAs/GaAlAs, GaAs/GaAlAs, and Si.
    Źródło:
    Acta Physica Polonica A; 2005, 107, 1; 82-91
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Influence of Magnetic Field on Dark States in Transport through Triple Quantum Dots
    Autorzy:
    Wrześniewski, K.
    Weymann, I.
    Powiązania:
    https://bibliotekanauki.pl/articles/1032454.pdf
    Data publikacji:
    2017-07
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    73.23.-b
    73.21.La
    Opis:
    We theoretically study the electronic transport through a triple quantum dot system in triangular geometry weakly coupled to external metallic leads. By means of the real-time diagrammatic technique, the current and Fano factor are calculated in the lowest order of perturbation theory. The device parameters are tuned to such transport regime, in which coherent population trapping of electrons in quantum dots due to the formation of dark states occurs. The presence of such states greatly influences transport properties leading to a strong current blockade and enhanced, super-Poissonian shot noise. We consider both one- and two-electron dark states and examine the influence of magnetic field on coherent trapping in aforementioned states. When the system is in one-electron dark state, we observe a small shift of the blockade's region, whereas in the case of two-electron dark state, we show that strong magnetic field can lift the current blockade completely.
    Źródło:
    Acta Physica Polonica A; 2017, 132, 1; 108-111
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Tunneling of Interacting Fermions in 1D Systems
    Autorzy:
    Gendiar, A.
    Moško, M.
    Vagner, P.
    Németh, R.
    Powiązania:
    https://bibliotekanauki.pl/articles/2043712.pdf
    Data publikacji:
    2005-10
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    73.23.-b
    73.61.Ey
    Opis:
    Using the self-consistent Hartree-Fock approximation for spinless electrons at zero temperature, we study tunneling of the interacting electron gas through a single δ barrier in a finite one-dimensional wire connected to contacts. Our results exhibit features known from correlated many-body models. In particular, the conductance decays with the wire length as ∝ L$\text{}^{-2α}$, where the powerα is universal. We also show that a similar result for a wire conductance can be extracted from the persistent current (I) through theδ barrier in a one-dimensional ring, where it is known that I∝ L$\text{}^{-1-α}$.
    Źródło:
    Acta Physica Polonica A; 2005, 108, 4; 661-667
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Hartree-Fock Simulation of Persistent Current in Rings with Single Scatterer
    Autorzy:
    Németh, R.
    Moško, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/2044507.pdf
    Data publikacji:
    2005-11
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    73.23.-b
    73.61.Ey
    Opis:
    Using the self-consistent Hartree-Fock approximation for spinless electrons at zero temperature, we calculate the persistent current of the interacting electron gas in a one-dimensional ring containing a single δ barrier. Our results agree with correlated models like the Luttinger liquid model and lattice model with nearest-neighbor interaction. The persistent current is a sine-like function of magnetic flux. It decays with the ring length (L) faster than L$\text{}^{-1}$ and eventually like L$\text{}^{-α-1}$, where α>0 is universal.
    Źródło:
    Acta Physica Polonica A; 2005, 108, 5; 795-801
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Quantum-Interference Semiconductor Devices Revisited
    Autorzy:
    Figielski, T.
    Powiązania:
    https://bibliotekanauki.pl/articles/2027427.pdf
    Data publikacji:
    2001-06
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    73.23.-b
    85.30.De
    Opis:
    First, a simple semiclassical approach has been applied to the problem of a quantum phase acquired by an electron carrying both the charge and spin, which travels in an electromagnetic field. Basic hypothetical devices whose operation relies on the quantum interference, including spin-related interference, are discussed in the following. Finally, experimental results demonstrating two-beam interference in a planar quantum dot are presented.
    Źródło:
    Acta Physica Polonica A; 2001, 99, 6; 699-708
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Current Shot Noise and Bunching of Electrons in Multilevel Quantum Dots
    Autorzy:
    Michałek, G.
    Bułka, B.
    Powiązania:
    https://bibliotekanauki.pl/articles/1813512.pdf
    Data publikacji:
    2008-01
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    73.23.-b
    72.70.+m
    Opis:
    Currents and their fluctuations in multilevel quantum dots are studied theoretically in the limit of sequential tunneling. The spin degrees of freedom, many-body electronic states (singlet and triplet) as well as relaxation processes between the levels of the quantum dots are considered. In general, due to the rapid relaxation processes the shot noise is sub-Poissonian, however for a large polarization of the outgoing currents from the singlet and triplet states one gets the super-Poissonian type of the shot noise due to the bunching of tunneling events.
    Źródło:
    Acta Physica Polonica A; 2008, 113, 1; 27-30
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Thermoelectric Transport through the Double Quantum Dot in the Sequential Tunneling Regime
    Autorzy:
    Szukiewicz, B.
    Wysokiński, K.
    Powiązania:
    https://bibliotekanauki.pl/articles/1195458.pdf
    Data publikacji:
    2014-11
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    73.23.-b
    73.63.Kv
    73.23.Hk
    Opis:
    The charge and spin thermoelectric transport in the system composed of a central molecule in contact with two normal electrodes in an external magnetic field of the Zeeman type have been studied. Such system can support pure spin current for applications in spintronics. By appropriate gate tuning of each of the dots it is possible to electrically control the direction of the spin current or tune the device operating as a thermoelectric generator to optimal performance.It has been shown that the device is poor energy converter in the parameter region where its thermoelectric figure of merit attains very large values.
    Źródło:
    Acta Physica Polonica A; 2014, 126, 5; 1159-1162
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Coherent Transport through Systems of Coupled Quantum Dots
    Autorzy:
    Trocha, P.
    Barnaś, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/2047730.pdf
    Data publikacji:
    2007-08
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    73.23.-b
    73.21.La
    73.23.Hk
    Opis:
    Spin-dependent electronic transport through two coupled single-level quantum dots attached to ferromagnetic leads with parallel and antiparallel magnetizations is analyzed theoretically. The intra-dot Coulomb correlation is taken into account, while the inter-dot Coulomb repulsion is omitted. Conductance and tunnel magnetoresistance associated with magnetization rotation are calculated by the nonequilibrium Green function technique. The relevant Green functions are derived by the equation of motion method in the Hartree-Fock approximation. The dot occupation numbers and the Green functions are calculated self-consistently. The interference effects in electronic transport through quantum dots are analyzed in two different configurations. It is shown that the Fano resonance in conductance can be observed even for vanishing inter-dot hopping parameter t. The interplay of the interference effects and the Coulomb interactions in quantum dots is also analyzed.
    Źródło:
    Acta Physica Polonica A; 2007, 112, 2; 473-480
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Electron Transport through Double Quantum Dots with Interdot Coulomb Repulsion
    Autorzy:
    Sztenkiel, D.
    Świrkowicz, R.
    Powiązania:
    https://bibliotekanauki.pl/articles/2047016.pdf
    Data publikacji:
    2006-09
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    73.23.-b
    73.21.La
    73.23.Hk
    Opis:
    Electron transport through a system of two quantum dots connected in series is studied theoretically with the use of non-equilibrium Green function formalism based on the equation of motion method. Each dot is described by the one-level Anderson Hamiltonian and interdot Coulomb interactions in the form of the Hubbard-like term are taken into account. The electric current and occupation numbers are calculated with the use of two different approaches. The results of the methods are compared and discussed in detail. Strong asymmetry of I-V characteristics with respect to bias voltage reversal are obtained when energy levels of the dots are not aligned.
    Źródło:
    Acta Physica Polonica A; 2006, 110, 3; 389-394
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Electron Transport through Double Quantum Dot System with Inter-Dot Coulomb Interaction
    Autorzy:
    Sztenkiel, D.
    Świrkowicz, R.
    Powiązania:
    https://bibliotekanauki.pl/articles/2047295.pdf
    Data publikacji:
    2007-03
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    73.23.-b
    73.21.La
    73.23.Hk
    Opis:
    A theoretical approach to a problem of electron transport through double quantum dot systems based on non-equilibrium Green function formalism using equation of motion method is presented. I-V characteristics and differential conductance are calculated and discussed in detail in the intermediate regime with tunneling rate between the quantum dots comparable to coupling constants with external electrodes. Effects of inter-dot Coulomb correlations are studied for various values of interaction parameter U. It is shown that the interaction influences transport properties in a pronounced way and apart from the simple Coulomb blockade additional effects can be obtained. When energy levels of two quantum dots are not aligned, the asymmetry in conductance characteristics is closely related to a voltage dependence of population numbers in both quantum dots. For a one bias polarization electrons are well localized in quantum dots in a low voltage region, whereas for the opposite one they are partly delocalized.
    Źródło:
    Acta Physica Polonica A; 2007, 111, 3; 361-372
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    On the Quantum Transport through an Asymmetric Aharonov-Bohm Ring with Rashba Spin-Orbit Interaction
    Autorzy:
    Baltateanu, D.
    Powiązania:
    https://bibliotekanauki.pl/articles/1492777.pdf
    Data publikacji:
    2011-12
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    73.23.-b
    71.70.Ej
    73.23.Ad
    Opis:
    The transmission amplitude through an asymmetric Aharonov-Bohm ring is derived analytically, in the presence of the Rashba spin-orbit interaction. For this purpose, one resorts to the transfer matrix method. The conductance is established in terms of the Landauer formalism and it is analyzed for different values of the asymmetry and ring-lead coupling parameters. A theoretical proposal to use the asymmetric ring like a spin filtering device is discussed, by an adequate tuning of the Aharonov-Bohm and Aharonov-Casher phases (via the magnetic field and the Rashba parameter).
    Źródło:
    Acta Physica Polonica A; 2011, 120, 6; 1047-1055
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Electron Transport in Magnetic Quantum Point Contacts
    Autorzy:
    Pietsch, T.
    Egle, S.
    Espy, C.
    Strigl, F.
    Scheer, E.
    Powiązania:
    https://bibliotekanauki.pl/articles/1490057.pdf
    Data publikacji:
    2012-02
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    73.23.-b
    72.25.-b
    73.63.-b
    Opis:
    In recent years, the fabrication of novel building blocks for quantum computation- and spintronics devices gained significant attention. The ultimate goal in terms of miniaturization is the creation of single-atom functional elements. Practically, quantum point contacts are frequently used as model systems to study the fundamental electronic transport properties of such mesoscopic systems. A quantum point contact is characterised by a narrow constriction coupling two larger electron reservoirs. In the absence of a magnetic field, the conductance of these quantum point contacts is quantised in multiples of $2 e^2//h$, the so-called conductance quantum $(G_0)$. However, in the presence of magnetic fields the increased spin-degeneracy often gives rise to a deviation from the idealized behaviour and therefore leads to a change in the characteristic conductance of the quantum point contact. Herein, we illustrate the complex magnetotransport characteristics in quantum point contacts and magnetic heterojunctions. The theoretical framework and experimental concepts are discussed briefly together with the experimental results as well as potential applications.
    Źródło:
    Acta Physica Polonica A; 2012, 121, 2; 401-409
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Different Quantization Mechanisms in Single-Electron Pumps Driven by Surface Acoustic Waves
    Autorzy:
    Utko, P.
    Gloos, K.
    Bindslev Hansen, J.
    Sørensen, C.
    Lindelof, P.
    Powiązania:
    https://bibliotekanauki.pl/articles/2047039.pdf
    Data publikacji:
    2006-09
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    73.23.-b
    72.50.+b
    73.21.La
    Opis:
    We have studied the acoustoelectric current in single-electron pumps driven by surface acoustic waves. We have found that in certain parameter ranges two different sets of quantized steps dominate the acoustoelectric current versus gate-voltage characteristics. In some cases, both types of quantized steps appear simultaneously though at different current values, as if they were superposed on each other. This could indicate two independent quantization mechanisms for the acoustoelectric current.
    Źródło:
    Acta Physica Polonica A; 2006, 110, 3; 403-408
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Theoretical Studies of Quantum Interference in Electronic Transport through Carbon Nanotubes
    Autorzy:
    Babiaczyk, W. I.
    Bułka, B. R.
    Powiązania:
    https://bibliotekanauki.pl/articles/2035583.pdf
    Data publikacji:
    2002
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    72.25.-b
    73.23.-b
    73.63.Fg
    Opis:
    We performed studies of coherent electronic transport through a single walled carbon nanotube. In the calculations multiple scattering on the contacts and interference processes were taken into account. Conductance is a composition of contributions from different channels. We studied also spin-dependent transport in the system with ferromagnetic electrodes. The magnetoresistance is large and shows large oscillations, it can be even negative in some cases.
    Źródło:
    Acta Physica Polonica A; 2002, 102, 4-5; 597-602
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Zero-Bias Anomaly in Magnetic Tunnel Junctions
    Autorzy:
    Yang, H.
    Yang, S.
    Ilnicki, G.
    Martinek, J.
    Parkin, S.
    Powiązania:
    https://bibliotekanauki.pl/articles/1536909.pdf
    Data publikacji:
    2010-08
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    73.21.La
    73.23.-b
    73.22.-f
    Opis:
    We present experimental results, which may indicate the possibility of the coexistence of the Kondo effect and ferromagnetism in macroscopic planar magnetic tunnel junctions with a layer of nanodots inside tunnel barriers. A conductance double peak structure was observed. Magnetic field dependence of the splitting of a conductance peak, and temperature evolution of the conductance curves are well explained from the theoretical point of view according to the predictions of the Kondo physics and cotunneling in the Anderson quantum dot coupled to ferromagnetic leads.
    Źródło:
    Acta Physica Polonica A; 2010, 118, 2; 316-318
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Spin-Dependent Transport through SU(4) Kondo Dot in the Presence of Spin-Flip Processes
    Autorzy:
    Krychowski, D.
    Lipiński, S.
    Powiązania:
    https://bibliotekanauki.pl/articles/1534863.pdf
    Data publikacji:
    2010-11
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    73.22.-f
    73.23.-b
    73.63.Fg
    Opis:
    The spin-resolved current of carbon nanotube quantum dot coupled to ferromagnetic electrodes and influenced by spin-flip scattering is studied in the Kondo regime by the equation of motion method.
    Źródło:
    Acta Physica Polonica A; 2010, 118, 5; 955-956
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Electrostatic Gates for GaN/AlGaN Quantum Point Contacts
    Autorzy:
    Czapkiewicz, M.
    Cywiński, G.
    Dybko, K.
    Siekacz, M.
    Wolny, P.
    Gierałtowska, S.
    Guziewicz, E.
    Skierbiszewski, C.
    Wróbel, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/1403637.pdf
    Data publikacji:
    2012-12
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    73.40.Qv
    73.61.Ng
    73.23.-b
    Opis:
    We report on AlGaN/GaN quantum point contacts fabricated by using e-beam lithography and dry ion etching. The tunable nano-constrictions are defined by the integration of side and top gates in a single device. In this configuration, the planar gates are located on the both sides of a quantum channel and the metallic top gates, which cover the active region, are separated from the substrate by an insulating and passivating layers of $HfO_2$ or $Al_2O_3//HfO_2$ composite. The properties of devices have been tested at T = 4.2 K. For side gates we have obtained a very small surface leakage current $I_g < 10^{-11}$ A at gate voltages $|V_g|$ < 2 V, however, it is not enough to close the quantum channel. With top gates we have been able to reach the pinch-off voltage at $V_g$ = - 3.5 V at a cost of $I_g ≈ 10^{-6} A$, which has been identified as a bulk leakage current.
    Źródło:
    Acta Physica Polonica A; 2012, 122, 6; 1026-1028
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Kondo Effect in Carbon Nanotube Quantum Dot in a Magnetic Field
    Autorzy:
    Krychowski, D.
    Lipiński, S.
    Powiązania:
    https://bibliotekanauki.pl/articles/1810539.pdf
    Data publikacji:
    2009-01
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    73.22.-f
    73.23.-b
    73.63.Fg
    Opis:
    The out-of-equilibrium electron transport of carbon nanotube semiconducting quantum dot placed in a magnetic field is studied in the Kondo regime by means of the non-equilibrium Green functions. The equation of motion method is used. For parallel magnetic field the Kondo peak splits into four peaks, following the simultaneous splitting of the orbital and spin states. For perpendicular field orientation the triple peak structure of density of states is observed with the central peak corresponding to orbital Kondo effect and the satellites reflecting the spin and spin-orbital fluctuations.
    Źródło:
    Acta Physica Polonica A; 2009, 115, 1; 293-295
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Magnetoresistance in Graphene-Based Ferromagnetic/ Rashba Barrier/Ferromagnetic Heterojunction
    Autorzy:
    Mohammadpour, H.
    Hasanirokh, K.
    Powiązania:
    https://bibliotekanauki.pl/articles/1191228.pdf
    Data publikacji:
    2016-01
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    72.80.Vp
    73.23.-b
    73.22.Pr
    Opis:
    The quantum tunnelling of spin-polarized electrons through a Rashba barrier on a single layer graphene is studied by the scattering matrix method. It is shown that the magnetoresistance, defined as the difference between conductance at the presence and absence of the Rashba spin-orbit interaction, oscillates with the intensity of interaction. These oscillations are also observed in the conductance versus the potential energy of the barrier.
    Źródło:
    Acta Physica Polonica A; 2016, 129, 1; 75-78
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Statistical Investigation of Current-Voltage Characterization in Single Molecule-Metal Junctions
    Autorzy:
    Kirchner, T.
    Briechle, B.
    Scheer, E.
    Wolf, J.
    Huhn, T.
    Erbe, A
    Powiązania:
    https://bibliotekanauki.pl/articles/1490078.pdf
    Data publikacji:
    2012-02
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    73.23.-b
    73.63.Rt
    81.07.Nb
    Opis:
    We show statistical measurements of single molecule-metal contacts using the mechanically controllable break junction technique. The measurements are carried out in a solvent, in order to allow in situ binding of the molecules to the metallic contacts during the measurements. Statistics is gathered by opening and closing the junctions repeatedly and recording current-voltage characteristics at various stages of the opening and closing curves. By modeling the data with a single level model we can extract parameters such as the position of the molecular energy level, which carries the current, and the coupling between the metal and the molecule. In first experiments we use this method to characterize different anchoring groups, which mediate the mechanical and electrical coupling between the metallic electrodes and the molecules. We use tolane molecules, which are structurally simple, as model systems for this purpose.
    Źródło:
    Acta Physica Polonica A; 2012, 121, 2; 410-415
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Interference Effects in Three-Terminal Hybrid Systems with Quantum Dots
    Autorzy:
    Michałek, G.
    Bułka, B.
    Powiązania:
    https://bibliotekanauki.pl/articles/1403609.pdf
    Data publikacji:
    2012-12
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    73.63.Kv
    74.45.+c
    73.23.-b
    Opis:
    Conductance in a three-terminal hybrid system with two quantum dots is analyzed. Our attention is focused on an influence of decoherence on interference effects in the Andreev transport. In particular, we have found that a change of coupling to the third electrode can strongly modify a shape of the Fano-type resonances. This effect is due to activation of nonlocal Andreev reflection (CAR) processes.
    Źródło:
    Acta Physica Polonica A; 2012, 122, 6; 981-983
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Spin Dependent Fano Resonances in a Rashba System with Coulomb Interactions
    Autorzy:
    Stefański, P.
    Powiązania:
    https://bibliotekanauki.pl/articles/2048075.pdf
    Data publikacji:
    2011-05
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    73.23.-b
    72.25.Dc
    73.40.Sx
    Opis:
    The effects of interplay of interference of quantum mechanical electron waves and their mutual Coulomb interactions are investigated in the device composed of interacting quantum dot attached to polarized leads via quantum point contacts with the Rashba interaction. The Zeeman-split dot sub-levels form two interfering channels and as a result spin dependent Fano resonances arise in the conductance through the system. The Coulomb repulsion between the channels modifies the width and shape of the Fano resonances as compared to the non-interacting case. We formulate the Fano expression dependent on the dot's occupancy regulated by the Coulomb interactions.
    Źródło:
    Acta Physica Polonica A; 2011, 119, 5; 644-647
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Andreev Transport in Double Quantum Dot Cooper Pair Splitters in the Presence of External Magnetic Field
    Autorzy:
    Trocha, P.
    Weymann, I.
    Powiązania:
    https://bibliotekanauki.pl/articles/1386830.pdf
    Data publikacji:
    2015-02
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    73.23.-b
    73.21.La
    74.45.+c
    Opis:
    The effect of external magnetic field on the transport properties of double quantum dots coupled to normal and superconducting leads is studied by means of the real-time diagrammatic technique in the sequential tunneling regime. This device works as a gate-controlled Cooper pair splitter. We focus on the transport regime where the current is blocked due to the spin triplet blockade. It is shown that external magnetic field can modify the Andreev current and differential conductance. In particular, magnetic field can suppress the negative differential conductance associated with the triplet blockade.
    Źródło:
    Acta Physica Polonica A; 2015, 127, 2; 502-504
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Aharonov-Bohm Effect and Valley Polarization in Nanoscopic Graphene Rings
    Autorzy:
    Rycerz, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/1810559.pdf
    Data publikacji:
    2009-01
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    73.23.-b
    73.63.Rt
    85.35.Ds
    Opis:
    The conductance of an Aharonov-Bohm interferometer is studied in a tight-binding model of graphene. Two point contacts with zigzag edges, which function as valley filters, are connected by a ring with an irregular boundary. We find that the narrowest rings show strong current suppression and nearly sinusoidal magnetoconductance oscillations, whereas for wide rings higher harmonics are equally represented. In the intermediate width range, oscillations with a basic periodicity are suppressed when two valley filters have opposite polarity, while higher harmonics are unaffected. The effect is interpreted in terms of a relatively weak intervalley scattering in the system.
    Źródło:
    Acta Physica Polonica A; 2009, 115, 1; 322-325
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Current Suppression in Transport Through Triple Quantum Dots Coupled to Ferromagnetic Leads
    Autorzy:
    Wrześniewski, K.
    Weymann, I.
    Powiązania:
    https://bibliotekanauki.pl/articles/1386617.pdf
    Data publikacji:
    2015-02
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    73.23.-b
    73.21.La
    85.75.-d
    Opis:
    We consider transport through triple quantum dot system in a triangular geometry weakly coupled to external ferromagnetic leads. The real-time diagrammatic technique in the lowest order perturbation theory is used to calculate the current and Fano factor in the parallel and antiparallel magnetic configuration of the system as well as the resulting tunnel magnetoresistance (TMR). We focus on the transport regime where the current is suppressed and show that it can lead to negative differential conductance and large super-Poissonian shot noise, which are present in both magnetic configurations. Furthermore, we show that for voltages where the system is trapped in a one-particle dark state the TMR becomes suppressed, while for two-particle blockade, the TMR is much enhanced.
    Źródło:
    Acta Physica Polonica A; 2015, 127, 2; 460-462
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Spin-Polarized Current in Coulomb Blockade and Kondo Regime
    Autorzy:
    Ogrodnik, P.
    Świrkowicz, R.
    Powiązania:
    https://bibliotekanauki.pl/articles/2047683.pdf
    Data publikacji:
    2007-08
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    73.23.-b
    73.21.La
    85.75.-d
    Opis:
    Spin-polarized electron transport through a single-level quantum dot attached to ferromagnetic and non-magnetic leads is studied with the use of the non-equilibrium Green function technique. Current polarization is investigated in dependence on parameters which characterize the device: the lead's polarization, a position of the dot energy level compared to the Fermi level in electrodes, and the Zeeman splitting of the dot level in an external magnetic field applied to the dot. Calculations were performed in two transport regimes: the Coulomb blockade regime with correlation effects treated within the Hartree-Fock approximation and the Kondo regime with a more rigorous approach to many-body effects at low temperatures.
    Źródło:
    Acta Physica Polonica A; 2007, 112, 2; 295-300
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Kondo-Fano Effect in Double Quantum Dot Side Attached to a Pair of Wires
    Autorzy:
    Krychowski, D.
    Lipiński, S.
    Powiązania:
    https://bibliotekanauki.pl/articles/1386758.pdf
    Data publikacji:
    2015-02
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    72.10.Fk
    73.21.-b
    73.22.-f
    73.23.-b
    Opis:
    Electron tunneling through a double quantum dot side coupled to a pair of leads is examined in finite-U slave boson mean field approach. Both the two-impurity Kondo regime at half filling and one-and three-electron Kondo effects are analyzed. Special attention is paid to the case when one of the dots is coupled to ferromagnetic lead and another to nonmagnetic. Depending on the gate voltage, the same or opposite sign of polarizations of conductance of the leads is observed.
    Źródło:
    Acta Physica Polonica A; 2015, 127, 2; 487-489
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Andreev Transport through a Magnetic Molecule Weakly Coupled to Ferromagnetic Leads
    Autorzy:
    Pawlicki, F.
    Weymann, I.
    Powiązania:
    https://bibliotekanauki.pl/articles/1030385.pdf
    Data publikacji:
    2018-03
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    73.23.-b
    74.45.+c
    75.50.Xx
    Opis:
    The Andreev transport through a single molecular magnet coupled to two external ferromagnetic leads and one superconducting electrode is studied theoretically by means of the real-time diagrammatic technique. The calculations are performed by including the sequential tunneling processes between the molecule and ferromagnetic leads, while the coupling to superconductor can be arbitrary. We analyze the dependence of the Andreev current and tunnel magnetoresistance on various intrinsic parameters of the molecule. The superconducting proximity effect results in the formation of molecular Andreev bound states. We show that the transport behavior depends greatly on the type of internal exchange interaction of the molecule, which can lead to corresponding sign changes of the tunnel magnetoresistance of the device.
    Źródło:
    Acta Physica Polonica A; 2018, 133, 3; 594-596
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Tunneling through the Quantum Dot Coupled to Incoherent Superconductor
    Autorzy:
    Donabidowicz, A.
    Domański, T.
    Powiązania:
    https://bibliotekanauki.pl/articles/2047329.pdf
    Data publikacji:
    2007-05
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    73.23.-b
    74.20.Fg
    74.45.+c
    Opis:
    We study the equilibrium and non-equilibrium properties of the strongly correlated quantum dot coupled between normal and superconducting leads. The effect of electron pair coherence, Coulomb interactions, and d-wave anisotropy of the order parameter are discussed with a particular account of their influence on a charge tunneling through the quantum dot.
    Źródło:
    Acta Physica Polonica A; 2007, 111, 5; 671-682
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Tunneling through the Quantum Dot Coupled between Normal and Superconducting Leads
    Autorzy:
    Donabidowicz, A.
    Domański, T.
    Wysokiński, K. I.
    Powiązania:
    https://bibliotekanauki.pl/articles/2047369.pdf
    Data publikacji:
    2007-08
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    73.23.-b
    74.20.Fg
    74.45.+c
    Opis:
    We study the charge tunneling via the quantum dot coupled to normal and superconducting leads, where the superconducting electrode has either an isotropic or anisotropic (of d-wave symmetry) energy gap. We use the single impurity Anderson model and apply the nonequilibrium Green function formalism to determine the differential tunneling conductance. The influence of the proximity effect between the quantum dot and superconductor on the transport properties of the system manifests itself in the Andreev conductance.
    Źródło:
    Acta Physica Polonica A; 2007, 112, 2; 157-160
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Electronic Transport through a Bending Contact
    Autorzy:
    Schröter, U.
    Powiązania:
    https://bibliotekanauki.pl/articles/2044664.pdf
    Data publikacji:
    2006-03
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    73.23.-b
    74.50.+r
    74.45.+c
    Opis:
    The so-called "break-junction technique" allows us to realize contacts only single-atom in diameter at their thinnest point. Electronic transport through such narrow constrictions shows a quantum mechanical signature which is well described in a transport channel picture. Each individual contact is characterized by an ensemble of channel transmission probabilities. Preferred total conductance values as well as the number of channels, however, turn out to be universal for the material investigated, despite the lack of control of the exact contact geometry.
    Źródło:
    Acta Physica Polonica A; 2006, 109, 3; 305-310
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Entanglement Detection by Current Measurements in Double Quantum Dot System
    Autorzy:
    Busz, P.
    Rożek, P.
    Tomaszewski, D.
    Martinek, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/1386781.pdf
    Data publikacji:
    2015-02
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    03.67.Mn
    03.67.Bg
    73.23.-b
    Opis:
    The development of quantum computing in quantum dots systems requires highly efficient and continuous solid-state source of spatially separated spin-entangled electrons. One of the approaches is a use of double quantum dot system connected to superconducting lead, where Cooper pairs provide a source of naturally entangled electrons. Apart from the source, an useful tool for detection of quantum entanglement is needed. We present entanglement detection by the ferromagnetic electrodes using entanglement witness operator method and direct measurement of spin polarized current in the system. We investigate requirements that have to be fulfilled by ferromagnetic detectors.
    Źródło:
    Acta Physica Polonica A; 2015, 127, 2; 490-492
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Entanglement Detection with Non-Ideal Ferromagnetic Detectors
    Autorzy:
    Rożek, P.
    Busz, P.
    Kłobus, W.
    Tomaszewski, D.
    Grudka, A.
    Baumgartner, A.
    Schönenberger, C.
    Martinek, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/1386794.pdf
    Data publikacji:
    2015-02
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    03.67.Mn
    03.67.Bg
    73.23.-b
    Opis:
    Entangled states are essential in basics quantum communication protocols and quantum cryptography. Ferromagnetic contacts can work as a spin detector, giving possibility of converting information about electron spin to the electric charge, and therefore, detection of entangled states with the electric current measurements is possible. Method of confirming entanglement with non-ideal detectors is presented, the impact of decoherence and noise on states and quality of entanglement is discussed. Entanglement witness (EW) operator method is compared with the CHSH inequalities approach. Required spin polarization for the EW is lower than for the CHSH inequalities. System with asymmetric spin polarizations of detectors was analyzed, including the CHSH inequalities and the EW method.
    Źródło:
    Acta Physica Polonica A; 2015, 127, 2; 493-495
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Subgap Current through the Strongly Correlated Quantum Dot Hybridized with the Normal and Superconducting Leads
    Autorzy:
    Domański, T.
    Donabidowicz, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/1810301.pdf
    Data publikacji:
    2009-01
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    73.23.-b
    74.20.Fg
    74.45.+c
    Opis:
    We investigate charge tunneling through the strongly correlated quantum dot placed between the metallic and superconducting leads. For small voltages |V| ≤ Δ/e applied across the junction the current is transmitted by the anomalous mechanism of the Andreev reflections. Such transport is sensitive to the strong Coulomb interactions which can be responsible for the charging effect and, at low temperatures, for appearance of the Kondo resonance. We analyze their signatures in the differential Andreev conductance.
    Źródło:
    Acta Physica Polonica A; 2009, 115, 1; 86-88
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Spin Thermoelectric Effects in Transport through a Two-Level Quantum Dot Coupled to Ferromagnetic Leads
    Autorzy:
    Karwacki, Ł.
    Trocha, P.
    Barnaś, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/1427587.pdf
    Data publikacji:
    2012-05
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    73.21.La
    73.23.-b
    73.63.Kv
    73.50.Lw
    Opis:
    We investigate spin thermoelectric effects in a two-level quantum dot attached to external ferromagnetic leads. The basic thermoelectric coefficients are calculated by means of the non-equilibrium Green functions approach in the mean field approximation for the Coulomb term. Specifically, we calculate spin-dependent thermopower (spin Seebeck coefficient) and the charge thermopower. These coefficients measure spin and charge voltage drops across the device, respectively. Moreover, the figure of merit and its spin analog (which measures the spin thermoelectric efficiency) are presented and discussed. We also show that the indirect (via the leads) coupling between the dot's levels can significantly enhance the thermoelectric effects.
    Źródło:
    Acta Physica Polonica A; 2012, 121, 5-6; 1207-1209
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    The In-Gap Charge Current through the Correlated Quantum Dot Hybridized with Superconductor
    Autorzy:
    Donabidowicz, A.
    Domański, T.
    Powiązania:
    https://bibliotekanauki.pl/articles/1812275.pdf
    Data publikacji:
    2008-07
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    73.23.-b
    74.20.Fg
    74.45.+c
    Opis:
    We explore the Andreev tunnelling through the strongly correlated quantum dot embedded between the normal and superconducting electrodes. For a small external voltage |eV| <$∆_s$ the electron arriving from the normal lead can be converted into a pair on the quantum dot and further propagates in the superconducting lead while simultaneously the hole is reflected back to the normal electrode. Conductance of such anomalous current is very sensitive to the particle-hole mixing of the quantum dot spectrum. We analyze the influence of the proximity effect and the Coulomb interactions on the differential Andreev conductance focusing on the extreme limit $∆_s$ → ∞.
    Źródło:
    Acta Physica Polonica A; 2008, 114, 1; 75-82
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Statistics of Conductance and Shot-Noise Power for Chaotic Cavities
    Autorzy:
    Sommers, H.-J.
    Wieczorek, W.
    Savin, D. V.
    Powiązania:
    https://bibliotekanauki.pl/articles/2047832.pdf
    Data publikacji:
    2007-10
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    73.23.-b
    73.50.Td
    05.45.Mt
    73.63.Kv
    Opis:
    We report on an analytical study of the statistics of conductance, g, and shot-noise power, p, for a chaotic cavity with arbitrary numbers N$\text{}_{1,2}$ of channels in two leads and symmetry parameterβ = 1, 2, 4. With the theory of Selberg's integral the first four cumulants of g and first two cumulants of p are calculated explicitly. We give analytical expressions for the conductance and shot-noise distributions and determine their exact asymptotics near the edges up to linear order in distances from the edges. For 0 < g < 1 a power law for the conductance distribution is exact. All results are also consistent with numerical simulations.
    Źródło:
    Acta Physica Polonica A; 2007, 112, 4; 691-697
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Electric Conductivity of Carbon Nanoparticles Stimulated by Electric Field
    Autorzy:
    Markowski, D.
    Kempiński, W.
    Kempiński, M.
    Trybuła, Z.
    Kaszyńska, K.
    Śliwińska-Bartkowiak, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/1535906.pdf
    Data publikacji:
    2010-09
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    73.22.Pr
    73.21.La
    73.23.Hk
    73.25.+i
    73.63.-b
    73.23.-b
    Opis:
    Host-guest interactions can be the unique method of spin manipulation in nanoscale. Strong changes in spin localization are generated when potential barriers between nanographitic units of activated carbon fibers are modified by interaction with adsorbed molecules. Stronger modifications occur when dipolar guest molecules are stimulated with external electric field. We report experimental results which show the influence of electric field on the spin localization in activated carbon fibers.
    Źródło:
    Acta Physica Polonica A; 2010, 118, 3; 457-458
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Singlet-Triplet Switching Induced by Electric Field in Triple Quantum Dots
    Autorzy:
    Łuczak, J.
    Bułka, B.
    Powiązania:
    https://bibliotekanauki.pl/articles/1427582.pdf
    Data publikacji:
    2012-05
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    71.10.-w
    33.57.+c
    73.23.-b
    73.63.Kv
    Opis:
    We analyze influence of an external electric field on magnetic properties of a triple quantum dot system in a triangular and linear geometry. The system contains four electrons and is described by an extended Hubbard model which includes electron correlations and exchange processes. The electric field leads to splitting of energy levels (the Stark effect) and to transition between the singlet and triplet states.
    Źródło:
    Acta Physica Polonica A; 2012, 121, 5-6; 1195-1197
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Spin Thermoelectric Effects in a Strongly Correlated Double Quantum Dot System
    Autorzy:
    Karwacki, Ł.
    Powiązania:
    https://bibliotekanauki.pl/articles/1386717.pdf
    Data publikacji:
    2015-02
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    73.23.-b
    73.63.Kv
    72.15.Qm
    85.35.Ds
    Opis:
    Spin thermoelectric effects through a strongly correlated double quantum dot system embedded in a Aharonov-Bohm ring coupled to two leads with Rashba spin-orbit coupling have been investigated theoretically by means of the finite-U slave-boson technique. This method provides a reliable description of electron transport through quantum dot systems in the low temperature regime T ≪ $T_{K}$, where $T_{K}$ is the so-called Kondo temperature. Particular emphasis is put on the possibility of the so-called spin Seebeck effect in such a system as a more sensitive probe of the Kondo state.
    Źródło:
    Acta Physica Polonica A; 2015, 127, 2; 478-480
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Thermoelectric and Interference Effects in a Kondo-Correlated Quantum Dot with Rashba Spin-Orbit Coupling
    Autorzy:
    Karwacki, Ł.
    Trocha, P.
    Barnaś, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/1399158.pdf
    Data publikacji:
    2013-11
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    73.23.-b
    73.63.Kv
    72.15.Qm
    85.35.Ds
    Opis:
    Thermoelectric effects in spin-polarized transport through a strongly correlated quantum dot coupled to two ferromagnetic leads is investigated theoretically by means of the finite-U slave boson technique. The dot is coupled to the leads both symmetrically via the spin-conserving tunneling processes and asymmetrically via spin-nonconserving Rashba-induced tunneling terms. The asymmetric coupling leads to various interference effects which modify transport properties. We have analyzed such thermoelectric coefficients like the electronic contribution to heat conductance κ, thermopower S, and thermoelectric efficiency ZT.
    Źródło:
    Acta Physica Polonica A; 2013, 124, 5; 901-904
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Dark States and Transport through Quantum Dots
    Autorzy:
    Tooski, S.
    Bułka, B.
    Powiązania:
    https://bibliotekanauki.pl/articles/1428598.pdf
    Data publikacji:
    2012-05
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    71.10.-w
    33.57.+c
    73.23.-b
    73.63.Kv
    Opis:
    We consider current through triple and quadruple quantum dot systems in an in-plane electric field and in the sequential tunneling regime. The electric field breaks symmetry of the system and can trap electron in a dark state in which current flow can completely be blocked. Consequently rotating the electric field, one can observe current oscillations and blockades due to dark state.
    Źródło:
    Acta Physica Polonica A; 2012, 121, 5-6; 1231-1233
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Linear and Non-Linear Response in T-Shaped Electron Waveguides
    Autorzy:
    Bek, M.
    Bułka, B.
    Wróbel, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/1791289.pdf
    Data publikacji:
    2009-11
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    73.23.-b
    73.63.Rt
    85.35.Ds
    85.35.Be
    Opis:
    We present theoretical studies of three-terminal ballistic junction in linear and non-linear regime. Various conductance and voltage dips and peaks are observed and their origin is explained as influence of the bend resistance and the threshold effect.
    Źródło:
    Acta Physica Polonica A; 2009, 116, 5; 829-831
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Andreev Conductance through a Quantum Dot Strongly Coupled to Ferromagnetic and Superconducting Leads
    Autorzy:
    Wójcik, K.P.
    Weymann, I.
    Powiązania:
    https://bibliotekanauki.pl/articles/1032390.pdf
    Data publikacji:
    2017-07
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    73.23.-b
    72.15.Qm
    74.45.+c
    72.25.-b
    Opis:
    We analyze the Andreev conductance through a quantum dot strongly coupled to one ferromagnetic and one superconducting lead. The transmission due to the Andreev reflection is obtained from the numerical renormalization group method. We show that at low temperatures, depending on the dot level position, the Andreev conductance exhibits a peak at zero bias due to the Kondo effect, which can be split by the exchange field due to spin-dependent coupling to ferromagnetic lead.
    Źródło:
    Acta Physica Polonica A; 2017, 132, 1; 143-145
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Spin and Charge Transport in a Magnetic Tunnel Junction with Magnetic Impurities Embedded in the Tunnel Barrier
    Autorzy:
    Misiorny, M.
    Barnaś, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/1402573.pdf
    Data publikacji:
    2015-08
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    72.10.Fk
    72.25.-b
    73.23.-b
    75.50.Xx
    Opis:
    Electronic transport in a nanoscopic magnetic tunnel junction with magnetic particles or magnetic impurity atoms/molecules embedded in the barrier is studied theoretically. The impurity Hamiltonian includes magnetic anisotropy of easy axis type with additional perpendicular term. The description takes into account both elastic tunneling processes as well as inelastic processes associated with a flip of electron spin.
    Źródło:
    Acta Physica Polonica A; 2015, 128, 2; 196-199
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Signatures of Transverse Magnetic Anisotropy in Transport through a Large-Spin Molecule in the Kondo Regime
    Autorzy:
    Misiorny, M.
    Weymann, I.
    Barnaś, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/1402574.pdf
    Data publikacji:
    2015-08
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    72.10.Fk
    72.25.-b
    73.23.-b
    75.50.Xx
    Opis:
    The effect of transverse magnetic anisotropy on spin-dependent transport through a large-spin molecule strongly tunnel-coupled to ferromagnetic electrodes is analyzed theoretically. In particular, we investigate whether it is possible to observe in transport signatures of oscillations of the ground-state doublet splitting due to the application of an external magnetic field along the molecule's hard axis. We show that magnetic field leads to revivals of the Kondo effect, with the Kondo temperature depending on the magnetic configuration of the device.
    Źródło:
    Acta Physica Polonica A; 2015, 128, 2; 200-203
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Thermoelectric Transport through a Quantum Dot Coupled to a Normal Metal and BCS Superconductor
    Autorzy:
    Krawiec, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/1812283.pdf
    Data publikacji:
    2008-07
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    73.63.Kv
    73.23.-b
    73.50.Lw
    72.15.Qm
    74.45.+c
    Opis:
    We discuss thermoelectric properties of a quantum dot coupled to one normal and one superconducting lead in the presence of the Kondo effect and the Andreev scattering. We will focus on conductance, thermal conductance, thermopower and related quantities like thermoelectric figure of merit which is a direct measure of the usefulness of the system for applications and the Wiedemann-Franz ratio which indicates if the system is in the Fermi liquid state. We will show that the superconductivity strongly modifies the thermal properties of the system. In particular, the thermopower is strongly enhanced near the superconducting transition temperature. Moreover, the Andreev reflections are suppressed due to strong on-dot Coulomb repulsion. The suppression of the Andreev reflections leads to a violation of the Wiedemann-Franz law and to a non-Fermi liquid ground state.
    Źródło:
    Acta Physica Polonica A; 2008, 114, 1; 115-122
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Asymmetry Induced Localization
    Autorzy:
    Kohler, H.
    Powiązania:
    https://bibliotekanauki.pl/articles/1399044.pdf
    Data publikacji:
    2013-12
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    05.30.-d
    03.65.Yz
    05.45.Mt
    73.23.-b
    Opis:
    We consider a two-level system, which couples via non-commuting operators to two independent oscillator baths. When the coupling is symmetric, the renormalized hopping matrix element is finite even for infinitely strong coupling strength. The two-level system is in a delocalized phase. For finite coupling strength a localization transition occurs for a critical asymmetry angle, which separates the localized from the delocalized phase. Using the method of flow equations we are able to monitor real time dynamics.
    Źródło:
    Acta Physica Polonica A; 2013, 124, 6; 1053-1059
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Fidelity Decay in Chaotical and Random Systems
    Autorzy:
    Kohler, H.
    Powiązania:
    https://bibliotekanauki.pl/articles/1492437.pdf
    Data publikacji:
    2011-12
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    05.30.-d
    03.65.Yz
    05.45.Mt
    73.23.-b
    Opis:
    Fidelity is the overlap of wave functions with the same initial state propagated in time by slightly different Hamiltonians. Its behavior depends crucially on the choice of the initial wave function state. We review two cases: first, the initial state is random. In this case a simple analytic relation with parametric spectral correlations can be established. The latter quantity is completely determined by the spectral data and can therefore be measured, without knowledge about the wave function. Second, the initial state is an eigenstate of the unperturbed system. In this case fidelity is identical to the survival probability. We find unexpected features like revival and non-ergodicity. In this case fluctuations around the mean are large and the full fidelity distribution becomes a non-trivial function. The full fidelity distribution can be calculated in the long time limit and for small perturbations.
    Źródło:
    Acta Physica Polonica A; 2011, 120, 6A; A-119-A-126
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Fano-Kondo Effect of Magnetic Impurity with Side-Coupled Graphene Flake
    Autorzy:
    Krychowski, D.
    Kopiński, J.
    Lipiński, S.
    Powiązania:
    https://bibliotekanauki.pl/articles/1201853.pdf
    Data publikacji:
    2014-07
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    73.22.Pr
    72.80.Vp
    73.23.-b
    72.15.Qm
    85.75.-d
    Opis:
    We examine transport through a spin-1/2 Kondo impurity, patterned between atomic scale electrodes in the presence of side-coupled nanographene flake. Impurity is attached to the edge of the flake, what allows to test the edge states. The Kotliar Ruckenstein slave boson approach is adopted to describe the strongly correlated impurity. We show that transport measurement of Fano-Kondo effect can serve as a spectroscopic probe of spin resolved graphene flake energy levels. The edge moments can be completely suppressed by gate voltage.
    Źródło:
    Acta Physica Polonica A; 2014, 126, 1; 202-203
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    New Semiconductor Devices
    Autorzy:
    Balestra, F.
    Powiązania:
    https://bibliotekanauki.pl/articles/1811906.pdf
    Data publikacji:
    2008-11
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    72.20.-i
    73.20.-r
    73.21.-b
    73.23.-b
    73.30.+y
    73.40.-c
    73.50.-h
    73.63.-b
    Opis:
    A review of recently emerging semiconductor devices for nanoelectronic applications is given. For the end of the international technology roadmap for semiconductors, very innovative materials, technologies and nanodevice architectures will be needed. Silicon on insulator-based devices seem to be the best candidates for the ultimate integration of integrated circuits on silicon. The flexibility of the silicon on insulator-based structure and the possibility to realize new device architectures allow to obtain optimum electrical properties for low power and high performance circuits. These transistors are also very interesting for high frequency and memory applications. The performance and physical mechanisms are addressed in single- and multi-gate thin film Si, SiGe and Ge metal-oxide-semiconductor field-effect-transistors. The impact of tensile or compressive uniaxial and biaxial strains in the channel, of high k materials and metal gates as well as metallic Schottky source-drain architectures are discussed. Finally, the interest of advanced beyond-CMOS (complementary MOS) nanodevices for long term applications, based on nanowires, carbon electronics or small slope switch structures are presented.
    Źródło:
    Acta Physica Polonica A; 2008, 114, 5; 945-974
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    On the 2D quantum tunneling
    Autorzy:
    Mohammadpour, H.
    Powiązania:
    https://bibliotekanauki.pl/articles/1159450.pdf
    Data publikacji:
    2016-09
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    72.10.-d
    72.10.Bg
    72.80.Vp
    72.90.+y
    73.21.Fg
    73.23.-b
    73.23.Ad
    73.40.Gk
    Opis:
    In this paper, we have solved a quantum tunneling problem for 2-dimensional systems, including electron gas and graphene. In spite of the one-dimensional scattering problems, in two dimensions, we observe phenomenon of tunneling at energies above the barrier. This effect is an analogue to the total internal reflection in optics. The scattering amplitudes inside the barrier region exhibit decaying behavior corresponding to optical evanescent-wave coupling, not only in energies below barrier height, but also above barrier. Velocity-selecting transmission, corresponding to angle-resolved beam filtering effect is one of the achievements of the paper. The famous Hartman effect which occurs normally at sub-barrier energies and has previously been studied for graphene is also addressed. The results manifest occurrence of the Hartman effect for over-barrier energies, as well.
    Źródło:
    Acta Physica Polonica A; 2016, 130, 3; 769-772
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Transport Through a Single-Molecule Transistor: Master-Equation Approach
    Autorzy:
    Donabidowicz-Kolkowska, A.
    Timm, C.
    Powiązania:
    https://bibliotekanauki.pl/articles/1431179.pdf
    Data publikacji:
    2012-04
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    73.23.Hk
    73.63.-b
    81.65.+h
    Opis:
    In the present work we employ the master-equation approach to describe the transport through a molecule located in the central region between two external electrodes. In contrast to the transport through a quantum dot, electron-phonon coupling should be taken into account for tunnelling through a molecule. The coupling results in the appearance of additional effects such as vibrational sidebands or, for the case of strong coupling, a suppression of the current at low bias voltage (Franck-Condon blockade). In contrast to previous studies, the transport properties are described by the density matrix calculated explicitly with diagonal and off-diagonal elements. The observed phenomena are discussed and compared to previous studies.
    Źródło:
    Acta Physica Polonica A; 2012, 121, 4; 730-732
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Phonon-Assisted Kondo Resonance in Spin-Dependent Transport through a Quantum Dot
    Autorzy:
    Świrkowicz, R.
    Wilczyński, M.
    Barnaś, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/1810522.pdf
    Data publikacji:
    2009-01
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    73.23.Hk
    73.63.Kv
    73.43.Qt
    72.25.-b
    Opis:
    Effects of local vibrational modes on electron transport through a quantum dot attached to ferromagnetic electrodes are studied in the Kondo regime by the non-equilibrium Green function formalism based on the equation of motion method. Differential conductance is calculated for parallel and antiparallel configurations of the leads' magnetic moments, and well defined Kondo resonance peaks and their phonon satellites are found. The influence of a compensating magnetic field on the peak positions is also discussed.
    Źródło:
    Acta Physica Polonica A; 2009, 115, 1; 272-274
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Signatures of Majorana States in Electron Transport through a Quantum Dot Coupled to a Topological Wire
    Autorzy:
    Stefański, P.
    Powiązania:
    https://bibliotekanauki.pl/articles/1384812.pdf
    Data publikacji:
    2015-02
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    73.63.-b
    73.23.Hk
    73.21.La
    74.78.Na
    Opis:
    We consider theoretically a system composed of a quantum dot coupled to a topological superconducting wire. The dot, being in Coulomb blockade (CB) regime is additionally coupled to the normal leads. The topological wire hosts Majorana states, which, as we show, characteristically modifies conductance through the dot. An unpaired Majorana state in the wire causes a unique temperature dependence of zero bias conductance vs. gate voltage. It decreases in-between CB peaks and on the sides of the peaks from the plateau at ~ e²/2h when temperature increases. At the same time conductance increases at the CB peak positions. It is accompanied by zero bias anomaly in differential conductance. For finite overlap of Majorana states in the wire the zero bias anomaly disappears. Instead, two characteristic Fano resonances of opposite symmetry appear, positioned mirror-symmetrically with respect to zero bias.
    Źródło:
    Acta Physica Polonica A; 2015, 127, 2; 198-200
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    The Puzzle of the 0.7 Anomaly in Conductance of Quantum Point Contact Reexamined
    Autorzy:
    Figielski, T.
    Powiązania:
    https://bibliotekanauki.pl/articles/1399104.pdf
    Data publikacji:
    2013-11
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    73.23.Ad
    73.61.Ey
    72.25.-b
    03.65.Ge
    Opis:
    A novel approach to the solution of the long-standing problem, called 0.7 anomaly in quantum point contact, is proposed. It is based on fundamental principles of quantum mechanics and can explain all main properties of the anomaly.
    Źródło:
    Acta Physica Polonica A; 2013, 124, 5; 841-842
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Spin Polarized Transport through Quantum Dots: Coulomb Blockade and Kondo Effect
    Autorzy:
    Barnaś, J.
    Świrkowicz, R.
    Wilczyński, M.
    Weymann, I.
    Martinek, J.
    Dugaev, V.
    Powiązania:
    https://bibliotekanauki.pl/articles/2036886.pdf
    Data publikacji:
    2003-08
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    72.25.-b
    73.23.Hk
    72.15.Qm
    Opis:
    Spin related effects in electronic transport through quantum dots, coupled via tunneling barriers to two metallic leads, are discussed from the point of view of fundamental physics and possible applications in spin electronics. The effects follow either from long spin relaxation time in the dots or from spin dependent tunneling through the barriers when the external leads are ferromagnetic. In the former case large nonequilibrium spin fluctuations in the dot can be induced by flowing current. These fluctuations modify transport characteristics, particularly the shape of the Coulomb steps. In the latter case electric current depends on magnetic configuration of the system, and tunnel magnetoresistance effect due to magnetization rotation can occur. Transport properties in the weak coupling regime are described perturbatively in the first (sequential) and second (cotunneling) orders. In the strong coupling regime, on the other hand, the equation of motion for nonequilibrium Green functions is used to calculate electric current at low temperatures, where the Kondo peak in conductance is formed in the zero bias regime. In symmetrical systems the Kondo peak is split in the parallel magnetic configuration, whereas no splitting occurs for the antiparallel alignment. Theoretical results are discussed in view of available experimental data.
    Źródło:
    Acta Physica Polonica A; 2003, 104, 2; 165-177
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Current-Induced Magnetic Dynamics in Asymmetric Ferromagnetic Single-Electron Devices
    Autorzy:
    Kowalik, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/1810537.pdf
    Data publikacji:
    2009-01
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    72.25.-b
    73.23.Hk
    85.75.-d
    Opis:
    The theoretical calculations of possible dynamics for a localized magnetic moment of the central electrode in ferromagnetic single-electron devices are presented. The spin-transfer torque from spin current absorbed by the central electrode is calculated. Thereafter, an in-plane component of spin torque is regarded during the integration of the Landau-Lifshitz-Gilbert equation and the time evolution of the localized magnetic moment of the central electrode is obtained. The necessary conditions for switching of the magnetic moment are discussed.
    Źródło:
    Acta Physica Polonica A; 2009, 115, 1; 290-292
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Spin Currents in Magnetic Nanostructures
    Autorzy:
    Dugaev, V.
    Bruno, P.
    Barnaś, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/1811907.pdf
    Data publikacji:
    2008-11
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    72.25.-b
    73.23.Ra
    75.75.+a
    Opis:
    We discuss some aspects of the problem of spin currents in magnetic nanostructures. One of them is related to the proper definition of the spin current and is generic for any electronic or magnetic system. Using the standard method related to the symmetry with respect to local spin transformations, we analyze the generation of equilibrium spin currents in inhomogeneous magnetic structures. As an example we consider the generation of persistent spin current in a mesoscopic ring.
    Źródło:
    Acta Physica Polonica A; 2008, 114, 5; 975-982
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Spin Polarized Transport through the Double-Dot System
    Autorzy:
    Sztenkiel, D.
    Świrkowicz, R.
    Powiązania:
    https://bibliotekanauki.pl/articles/2044544.pdf
    Data publikacji:
    2005-11
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    75.20.Hr
    72.15.Qm
    72.25.-b
    73.23.Hk
    Opis:
    Spin-dependent electron transport through two quantum dots in series attached to ferromagnetic electrodes is analyzed within the framework of the non-equilibrium Green function formalism. Regime of a weak coupling between the dots is investigated. I-V characteristics and tunnel magnetoresistance are calculated and discussed in detail.
    Źródło:
    Acta Physica Polonica A; 2005, 108, 5; 885-890
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Poor Mans Scaling Approach to the Kondo Effect in a Single Quantum Dot Asymmetrically Attached to Ferromagnetic Leads with Non-Collinear Magnetizations
    Autorzy:
    Wawrzyniak, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/1812020.pdf
    Data publikacji:
    2008-11
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    75.20.Hr
    72.15.Qm
    72.25.-b
    73.23.Hk
    Opis:
    The poor man's scaling technique is applied to the problem of electronic transport through a single quantum dot (with finite Coulomb repulsion) asymmetrically coupled to electrodes. The considered quantum dot is coupled to ferromagnetic electrodes, whose magnetic moments are non-collinear. The analysis and numerical illustration of spin splitting of the dot level as well as of the Kondo temperature on the coupling asymmetry is presented and discussed.
    Źródło:
    Acta Physica Polonica A; 2008, 114, 5; 1421-1424
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Poor Mans Scaling and Green Function Analysis of the Kondo Anomaly in Single-Level Quantum Dots
    Autorzy:
    Wawrzyniak, M.
    Świrkowicz, R.
    Wilczyński, M.
    Barnaś, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/1813883.pdf
    Data publikacji:
    2008-01
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    75.20.Hr
    72.15.Qm
    72.25.-b
    73.23.Hk
    Opis:
    Kondo effect in a single-level quantum dot attached to magnetic leads is studied theoretically by the "poor man's scaling" and non-equilibrium Green function methods. From the scaling equations we derive the Kondo temperature as a function of the model parameters - in particular as a function of the angle between magnetic moments. Transport characteristics, i.e. differential conductance and tunnel magnetoresistance associated with magnetization rotation, were calculated within the non-equilibrium Green function formalism based on the equation of motion method.
    Źródło:
    Acta Physica Polonica A; 2008, 113, 1; 553-556
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Electronic Transport through the Double-Dot System
    Autorzy:
    Świrkowicz, R.
    Sztenkiel, D.
    Powiązania:
    https://bibliotekanauki.pl/articles/2038086.pdf
    Data publikacji:
    2004-06
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    75.20.Hr
    72.15.Qm
    72.25.-b
    73.23.Hk
    Opis:
    Electron tunnelling through two quantum dots in series is theoretically studied. A limit of intermediate coupling between the dots is considered. The non-equilibrium Green function formalism is used to calculate electric current and mean number of electrons accumulated on the dots. Lesser and retarded Green functions are calculated in the Hartree-Fock approximation with the use of the equation of motion method. Current flowing through the system calculated in dependency on gate voltages shows two resonant peaks, each peak with two additional shoulders. I-V characteristics and differential conductance in a resonance and out of resonance cases are calculated and discussed.
    Źródło:
    Acta Physica Polonica A; 2004, 105, 6; 523-528
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Nonequilibrium Kondo Effect in a Single-Channel Quantum Dot Asymmetrically Coupled to Two Ferromagnetic Reservoirs
    Autorzy:
    Świrkowicz, R.
    Wilczyński, M.
    Barnaś, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/2037118.pdf
    Data publikacji:
    2004
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    75.20.Hr
    72.15.Qm
    72.25.-b
    73.23.Hk
    Opis:
    Nonequilibrium Kondo effect in a quantum dot asymmetrically coupled to two ferromagnetic metallic leads is analyzed theoretically. The nonequilibrium Green function technique is used to calculate density of states and electric current. The lesser and retarded (advanced) Green functions are calculated by the equation of motion method within a consistent approximation scheme. The case where one electrode is half-metallic is analyzed numerically in details.
    Źródło:
    Acta Physica Polonica A; 2004, 105, 1-2; 149-154
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-67 z 67

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