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Wyświetlanie 1-15 z 17
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:
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:
Si Multidot FETs for Single-Electron Transfer and Single-Photon Detection
Autorzy:
Tabe, M.
Nuryadi, R.
Moraru, D.
Burhanudin, Z.
Yokoi, K.
Ikeda, H.
Powiązania:
https://bibliotekanauki.pl/articles/1813190.pdf
Data publikacji:
2008-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.21.La
73.23.Hk
Opis:
Recently, there have been increasing demands for controlling individual electrons, photons, and dopants in developing nm scale Si devices. Our most recent results on Si single-electron nano-devices will be presented. We have demonstrated single-electron transfer in random-tunnel-junctions by a cycle of ac gate bias, detection of photons and detection of individual acceptor ions by Si single-hole transistor.
Źródło:
Acta Physica Polonica A; 2008, 113, 3; 811-814
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:
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:
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:
Analysis of the Kondo Resonance in a Single Quantum Dot Asymmetrically Coupled to Ferromagnetic Electrodes with Non-Collinear Magnetizations
Autorzy:
Wawrzyniak, M.
Powiązania:
https://bibliotekanauki.pl/articles/1810546.pdf
Data publikacji:
2009-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
72.15.Qm
73.21.La
73.23.Hk
Opis:
The Kondo effect is studied theoretically in the framework of the non-equilibrium Green function formalism. The system under consideration consists of a single quantum dot asymmetrically coupled to ferromagnetic electrodes, whose magnetic moments are non-collinear. The spin-dependent density of states, as well as the transport characteristics such as differential conductance and tunneling magnetoresistance through the system are obtained using the equation of motion method. Numerical illustration of the mentioned quantities for several magnetic configurations and coupling strengths is presented and discussed.
Źródło:
Acta Physica Polonica A; 2009, 115, 1; 303-305
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Coupled Multiphysics Models for the Analysis οf the Conduction and Valence Band Eigenenergies in Cylindrical Quantum Dots
Autorzy:
Prabhakar, S.
Takhtamirov, E.
Melnik, R.
Powiązania:
https://bibliotekanauki.pl/articles/1490797.pdf
Data publikacji:
2012-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.15.-m
73.21.La
62.23.Eg
Opis:
We develop a mathematical model for the analysis of conduction and valence band eigenenergy in quantum dots. We apply the model to study the band structure calculations of low dimensional semiconductor nanostructures such as wurtzite AlN/GaN quantum dots in cylindrical coordinates in presence of applied magnetic field along z-direction. We use a finite element method to solve the resulting model and to obtain eigenvalues and wave functions of cylindrical quantum dots. We provide details of the methodology of solution and appropriate boundary conditions. A special attention is given to the case of applied magnetic field along z-direction, we found localized eigenstates and wave functions in the conduction and valence bands for which our results open new possibilities for the design of the optoelectronics devices where the combination of electron-hole pairs can be used as tuning parameters.
Źródło:
Acta Physica Polonica A; 2012, 121, 1; 85-88
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Application of the Dot-Ring Nanostructure to Control Electrical Transport in the Coulomb Blockade Regime
Autorzy:
Janus-Zygmunt, I.
Kędzierska, B.
Gorczyca-Goraj, A.
Kurpas, M.
Maśka, M.
Zipper, E.
Powiązania:
https://bibliotekanauki.pl/articles/1376091.pdf
Data publikacji:
2014-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.23.Hk
73.21.La
73.22.-f
Opis:
Transport properties of a two-dimensional nanostructure composed of a quantum dot surrounded by a quantum ring (dot-ring nanostructure), are discussed. This complex system is a highly controllable object. Conduction through dot-ring nanostructure depends crucially on the coupling strength of its states to the electrodes, which is related to the spatial distribution of the electron's wave functions in dot-ring nanostructure. This distribution can be strongly modified, e.g., by the electrical gating so that the ground and excited states move between the inner dot and the outer ring. In this paper we show that this property can be used to control single-electron DC current through dot-ring nanostructure in the Coulomb blockade regime so that it can be used as a single electron transistor.
Źródło:
Acta Physica Polonica A; 2014, 126, 5; 1171-1173
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:
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:
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
Wyświetlanie 1-15 z 17

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