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1
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High Mobility 2D Electron Gas in CdTe/CdMgTe Heterostructures

100%
Karczewski G., Jaroszyński J., Kutrowski M., Barcz A., Wojtowicz T., Kossut J.
Acta Physica Polonica A
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1997
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vol. 92
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issue 4
829-832
EN
We report on iodine doping of molecular beam epitaxy (MBE)-grown Cd(Mn)Te quasi-bulk films and modulation-doped CdTe/Cd_{1-y}Mg_{y}Te two-dimensional (2D) single quantum well structures. Modulation doping with iodine of CdTe/Cd_{1-y}Mg_{y}Te structures resulted in fabrication of a 2D electron gas with mobility exceeding 10^{5} cm^{2}/(V s). This is the highest mobility reported in wide-gap II-VI materials.
2
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Density of States for Ballistic Electrons in Electric and Magnetic Fields

51%
Zawadzki W., Kubisa M.
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vol. 96
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issue 5
603-612
EN
The density of states for ballistic electrons in the presence of an electric field of almost arbitrary shape is calculated for one, two, and three dimensions using the semiclassical quantization in a finite sample. The semiclassical results are compared with these of the complete quantum treatment for a constant electric field. The case of crossed electric and magnetic fields is also considered and it is demonstrated that in this configuration the density of states exhibits a transition between magnetic and electric types of motion. Implications of this transition for the quantum Hall effect are mentioned.
3
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Composite Fermions and the Fractional Quantum Hall Effect

51%
Wójs A., Quinn J.
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vol. 96
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issue 5
593-602
EN
The mean field composite fermion picture successfully predicts low lying states of fractional quantum Hall systems. This success cannot be attributed to a cancellation between the Coulomb and Chern-Simons interactions beyond the mean field and solely depends on the short-range of the Coulomb pseudopotential in the lowest Landau level. The class of pseudopotentials for which the mean field composite fermion picture can be applied is defined. The success or failure of the mean field composite fermion picture in various systems (electrons in excited Landau levels, Laughlin quasiparticles, charged magnetoexcitons) is explained.
4
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Magnetic Translations for a Spatially Periodic Magnetic Field

51%
Florek W.
Acta Physica Polonica A
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2000
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vol. 97
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issue 4
619-628
EN
It is shown that in the case of a free electron in a spatially periodic magnetic field the concept of magnetic translations operators is still valid and, moreover, these operators can be defined in the same way as for a Bloch electron in a uniform magnetic field. The results can be a useful tool in the investigation of recently observed phenomena in 2D electron gas with spatially modulated density.
5
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Detection of Single Submillimeter-Wave Photons Using Quantum Dots

51%
Komiyama S., Astafiev O., Antonov V., Kutsuwa T.
Acta Physica Polonica A
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2000
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vol. 98
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issue 3
271-278
EN
Single-photon detection in a range of submillimeter waves (λ = 0.17-0.20 mm) is demonstrated by using lateral semiconductor quantum dots fabricated on a high-mobility GaAs/AlGaAs single heterostructure crystal. When a submillimeter photon is absorbed by the quantum dot while it is operated as a single-electron transistor, it switches on (or off) the conductance through the quantum dot. An incident flux of 0.1 photons/s on an effective detector area, (0.1 mm)^{2}, is detected with a 1 ms time resolution. The effective noise equivalent power is roughly estimated to reach on the order of 10^{-22} W/Hz^{1/2}, a value superior to the ever reported best values of conventional detectors by a factor more than 10^{4}.
6
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Skyrmions and the ν=1 Quantum Hall Ferromagnet

44%
Manfra M., Goldberg B., Pfeiffer L., West K.
Acta Physica Polonica A
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1997
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vol. 92
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issue 4
621-632
EN
Recent experimental and theoretical investigations have resulted in a shift in our understanding of the ν=1 quantum Hall state. There now exists a wealth of evidence that the excitation gap and the resulting quasiparticle spectrum at ν=1 are due predominately to the ferromagnetic many-body exchange interaction. A great variety of experimentally observed correlations at ν= 1 cannot be incorporated into a perturbative expansion around the single-particle model, a scheme long thought to describe the integral quantum Hall effect at filling factor 1. Theorists now refer to the ν=1 state as the quantum Hall ferromagnet. In this paper we review recent theoretical and experimental progress and detail our own optical investigations of the ν= 1 quantum Hall regime. The technique of magneto-absorption spectroscopy has proven to be powerful a probe of the occupancy of the lowest Landau level in the regime of 0.7<ν<1.3 about the spin gap. Additionally, we have performed simultaneous measurements of the absorption, photoluminescence and photoluminescence excitation spectra of the ν=1 state in order to elucidate the role of excitonic and relaxation effects in optical spectroscopy in the quantum Hall regime.
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