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Wyszukujesz frazę "73.21.Fg" wg kryterium: Temat


Tytuł:
Quasi-Particle Localization by Disorder in ν = 5/2 Fractional Quantum Hall State and Its Potential Application
Autorzy:
Goswami, P.
Powiązania:
https://bibliotekanauki.pl/articles/1418290.pdf
Data publikacji:
2012-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.21.Fg
Opis:
We consider the filling factor 5/2 fractional quantum Hall state of spin-polarized fermions in a dirty (mobility $μ_b \lt 10 m^2 V^{-1} s^{-1}$) bi-layer quantum well system.We show that the system undergoes a quantum phase transition from the effective two-component state to an effective single-component state, at fixed charge imbalance regulatory parameter $\Delta_{c}$ and constant layer separation, as the inter-layer tunneling strength $\Desta_\text{SAS}$ is increased. At finite and constant $\Delta_\text{SAS}$, a transition from the latter state to the former state is also possible upon increasing the parameter $\Delta_{c}$. We identify the order parameter to describe quantum phase transition as a pseudo-spin component and calculate this with the aid of the Matsubara propagators in the finite-temperature formalism. Our treatment is able to show that, at low temperature(< 0.1 K) and low value of charge imbalance regulatory parameter, there is a competition between the disorder and the inter-layer tunneling strength in the sample. The competition leads to the quasi-particle localization at low tunneling strength.
Źródło:
Acta Physica Polonica A; 2012, 122, 4; 741-747
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Polarization-Induced Band Inversion in In-Rich InGaN/GaN Quantum Wells
Autorzy:
Łepkowski, S.
Bardyszewski, W.
Rodak, D.
Powiązania:
https://bibliotekanauki.pl/articles/1195356.pdf
Data publikacji:
2014-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.21.Fg
73.22.Dj
Opis:
We theoretically study the polarization-induced band inversion phenomenon in c-plane In-rich InGaN/GaN quantum wells. Our calculations performed using the k·p method with the 8×8 Rashba-Sheka-Pikus Hamiltonian for the structures with the indium content between 90% and 100% show that the reordering of the conduction and valence bands occurs for the quantum well widths below the theoretical values of critical thickness for InGaN layers pseudomorphically grown on GaN substrates.
Źródło:
Acta Physica Polonica A; 2014, 126, 5; 1154-1155
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Inter-Landau Level Scattering Processes in Magnetic Field Assisted THz Quantum Cascade Laser
Autorzy:
Radovanović, J.
Daničić, A.
Milanović, V.
Indjin, D.
Ikonic, Z.
Powiązania:
https://bibliotekanauki.pl/articles/1503186.pdf
Data publikacji:
2011-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
72.10.-d
73.21.Fg
Opis:
We present a detailed analysis of GaAs/AlGaAs terahertz quantum cascade laser in the presence of an intense external magnetic field. One of the objectives in further development of THz quantum cascade laser is the realization of structures operating at higher temperatures. This is difficult to obtain as the operating photon emission energy is smaller than the longitudinal-optical phonon energy in the semiconductor material. With increased temperature, electrons in the upper radiative state gain sufficient in-plane energy to emit an longitudinal-optical phonon, which represents a non-radiative scattering and reduces the optical gain. By applying strong magnetic field, two-dimensional continuous energy subbands become split into series of discrete Landau levels, and at particular values of B it is possible to quench these non-radiative channels. Numerical simulations are performed on two-well design quantum cascade laser operating at 4.6 THz, implemented in GaAs/$Al_{0.15}Ga_{0.85}As$, and the magnetic field is perpendicular to the epitaxial layers. Strong oscillations of carrier lifetimes for the upper state of the laser transition, as a function of magnetic field are observed, which can be attributed to interface roughness scattering and longitudinal-optical phonon scattering between Landau levels.
Źródło:
Acta Physica Polonica A; 2011, 120, 2; 227-230
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Electron-Hole Distribution and Exciton Condensed Phase Formation in Semiconductor Quantum Wells
Autorzy:
Chernyuk, A. A.
Sugakov, V. I.
Powiązania:
https://bibliotekanauki.pl/articles/2046909.pdf
Data publikacji:
2006-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.35.Lk
73.21.Fg
Opis:
We study the development of ring luminescence of indirect excitons at macroscopical distances from the central excitation spot in quantum well structures. The Landau model for exciton condensation generalized for particles with finite lifetimes in conditions of inhomogeneous excitation is proposed. The transition between the fragmented and continuous rings and the temperature dependence of the effects are considered. The irradiation of the system by two spatially separated laser spots is simulated as well.
Źródło:
Acta Physica Polonica A; 2006, 110, 2; 169-174
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Crystal Orientation Dependence of the Fundamental Optical Transition in type-II W-Design Quantum Well Structures
Autorzy:
Ryczko, K.
Powiązania:
https://bibliotekanauki.pl/articles/1376073.pdf
Data publikacji:
2014-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.21.Fg
71.55.Eq
Opis:
Using a multiband k·p theory the band structure properties of type-II W-design AlSb/InAs/GaInSb/InAs/AlSb quantum wells on GaSb substrates of various crystallographic orientations have been investigated. Such structures are predicted for the emission in a broad range of mid infrared from below 3 μm to beyond 10 μm. The energy of the fundamental optical transition and the corresponding oscillator strength have been determined in function of the layer structure details and versus the substrate orientation. In addition, the resulting optical anisotropy in such type-II quantum wells has been derived.
Źródło:
Acta Physica Polonica A; 2014, 126, 5; 1149-1153
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Anisotropy of the Conductivity in the Asymmetric Quantum Wells
Autorzy:
Majchrowski, K.
Paśko, W.
Powiązania:
https://bibliotekanauki.pl/articles/1811959.pdf
Data publikacji:
2008-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
72.40.+w
73.21.Fg
Opis:
Gorbatsevich et al. and Kibis suggested that a number of interesting galvano-magnetic effects could be observed in quantum structures where the symmetry with respect to the space coordinates inversion and time-reversal are broken simultaneously. In the paper of Kibis for example, the infinite triangular quantum well in an external magnetic field was considered and the anisotropy of electron momentum transfer due to interaction with phonons was predicted. The role of magnetic field was to provide the time-invariance breaking. In this work we considered the effect of anisotropy of electron momentum transfer due to interaction with polarized light using more realistic model of finite triangular quantum well. This anisotropy leads to the anisotropy of the real part of photoconductivity and as it follows from our calculations, the effect though not very great, could be measurable for the attainable values of magnetic field B≈5 T and the widths of quantum well.
Źródło:
Acta Physica Polonica A; 2008, 114, 5; 1241-1246
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Quantum Cascade Laser Design for Tunable Output at Characteristic Wavelengths in the Mid-Infrared Spectral Range
Autorzy:
Daničić, A.
Radovanović, J.
Milanović, V.
Indjin, D.
Ikonić, Z.
Powiązania:
https://bibliotekanauki.pl/articles/1537879.pdf
Data publikacji:
2010-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
72.10.-d
73.21.Fg
Opis:
We present a method for systematic optimization of quantum cascade laser active region, based on the use of the genetic algorithm. The method aims at obtaining a gain-maximized structure, designed to emit radiation at specified wavelengths suitable for direct absorption by pollutant gasses present in the ambient air. After the initial optimization stage, we introduce a strong external magnetic field to tune the laser output properties and to slightly modify the emission wavelength to match the absorption lines of additional compounds. The magnetic field is applied perpendicularly to the epitaxial layers, thus causing two-dimensional continuous energy subbands to split into series of discrete Landau levels. This affects all the relevant relaxation processes in the structure and consequently the lifetime of carriers in the upper laser level. Furthermore, strong effects of band nonparabolicity result in subtle changes of the lasing wavelength at magnetic fields which maximize the gain, thus providing a path for fine-tuning of the output radiation properties. Numerical results are presented for GaAs/$Al_{x}Ga_{1-x}As$ based quantum cascade laser structures designed to emit at particular wavelengths in the mid-infrared part of the spectrum.
Źródło:
Acta Physica Polonica A; 2010, 117, 5; 772-776
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Charge Carrier Transport in Quantum Cascade Lasers in Strong Magnetic Field
Autorzy:
Radovanović, J.
Milanović, V.
Indjin, D.
Ikonić, Z.
Harrison, P.
Powiązania:
https://bibliotekanauki.pl/articles/1505456.pdf
Data publikacji:
2011-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
72.10.-d
73.21.Fg
Opis:
We have developed a comprehensive rate equations based model for calculating the optical gain in the active region of a quantum cascade laser in magnetic field perpendicular to the structure layers, which takes into account all the relevant scattering channels. The model is applied to gain-optimized quantum cascade laser active region, obtained by a systematic optimization procedure based on the use of genetic algorithm, which we have previously set up for designing novel structures and improving performance of existing ones. It has proven to be very efficient in generating optimal structures which emit radiation at specified wavelengths corresponding to absorption fingerprints of particular harmful pollutants found in the atmosphere. We also illustrate another interesting prospective application of quantum cascade laser-type structures: the design of metamaterials with tunable complex permittivity, based on amplification via intersubband transitions. In this case, the role of the magnetic field is to assist the attainment of sufficient optical gain (population inversion), necessary to effectively manipulate the permittivity and fulfill the conditions for negative refraction (left-handedness).
Źródło:
Acta Physica Polonica A; 2011, 119, 2; 99-102
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Photogalvanic Effect in Semiparabolic Quantum Well
Autorzy:
Majchrowski, K.
Paśko, W.
Tralle, I.
Powiązania:
https://bibliotekanauki.pl/articles/1791300.pdf
Data publikacji:
2009-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
72.40.+w
73.21.Fg
Opis:
In this work we studied the charge carriers behaviour in quantum structures where the symmetry with respect to space coordinates and time-reversal symmetry are broken simultaneously. As the model of such structures we considered finite semiparabolic quantum well (we considered earlier the case of triangular QW) placed in external magnetic field. We have shown by numerical analysis that the energy spectra of charge carriers in such structures are anisotropic with respect to in-plane (transverse) motion $ϵ_{n}( + k_{x})$ ≠ $ϵ_{n}(-k_{x})$. This leads to the anisotropy of charge carriers in-plane momentum transfer which, in its turn leads to the anisotropy of photoconductivity $σ( + k_{x})$ ≠ $σ(-k_{x})$ and as it follows from our calculations, the effect though not very great, could be measurable for the magnetic field of about few T.
Źródło:
Acta Physica Polonica A; 2009, 116, 5; 854-856
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Bychkov-Rashba Effect and g-Factor Tuning in Modulation Doped SiGe Quantum Wells
Autorzy:
Malissa, H.
Jantsch, W.
Mühlberger, M.
Schäffler, F.
Wilamowski, Z.
Draxler, M.
Bauer, P.
Powiązania:
https://bibliotekanauki.pl/articles/2038126.pdf
Data publikacji:
2004-06
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.21.Fg
85.75.-d
Opis:
We investigate the spin resonance of electrons in one-sided modulation doped Si$\text{}_{1-x}$Ge$\text{}_{x}$ (x=0-10%)) quantum wells defined by Si$\text{}_{0.75}$Ge$\text{}_{0.25}$ barriers. In such structures, the Bychkov-Rashba effect induces an effective magnetic field in the quantum well layer which causes anisotropy of both the g-factor and the spin coherence time. Evaluation of the Rashba coefficient as a function of x yields a monotonic increase. For x=5% the shift in the resonance field exceeds the ESR linewidth already, demonstrating the possibility to use this effect for g-factor tuning to select individual spins in an ensemble.
Źródło:
Acta Physica Polonica A; 2004, 105, 6; 585-590
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł

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