Modulation potential effects on the quantum magnetotransport in a two-dimensional electron gas.
Item
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Title
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Modulation potential effects on the quantum magnetotransport in a two-dimensional electron gas.
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Identifier
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AAI9820569
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identifier
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9820569
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Creator
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Park, Tae-ik.
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Contributor
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Adviser: Godfrey Gumbs
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Date
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1998
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Language
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English
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Publisher
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City University of New York.
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Subject
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Physics, Condensed Matter
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Abstract
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The quantum magnetotransport (QMT) coefficients of a two-dimensional electron gas (2DEG) in a perpendicular magnetic field for the 2D square array of modulated anti-dot (AD) and in quantum dot (QD)-limit potentials and 1D Quantum Wire (QW) are calculated in the low magnetic field region ({dollar}<{dollar}0.3 T) using the Kubo method. The model potential is modulated by controlling the steepness and its strength. The effect on the band part of all QMT coefficients are studied. Our analysis is based on how the sub Landau Level states sue to new magnetic Brillouin zone (MBZ) affect the QMT coefficients, how the cyclotron orbit and the scattering by the potential contribute to the QMT coefficients, and how the states near the Fermi level and below the Fermi level contribute to the QMT coefficients when the size and the strength of the modulated potential are changed.;The results for 2D modulation show that (i) Oscillations associated with the filling of sub Landau levels occur in {dollar}\rm\sigma\sbsp{lcub}xx{rcub}{lcub}(0){rcub}{dollar} and {dollar}\rm\sigma\sbsp{lcub}yx{rcub}{lcub}(0){rcub}{dollar} for the low modulation case. (ii) The effect of scattering by the AD potential is quite different from that by the dot potential. (iii) For a strong lateral superlattice AD potential, the longitudinal resistivity {dollar}\rm\rho\sbsp{lcub}xx{rcub}{lcub}(0){rcub}{dollar} has a double peak structure which depends on both the strength of the modulation potential as well as its slope. (iv) For both the AD and QD potentials, {dollar}\rm\rho\sbsp{lcub}xy{rcub}{lcub}(0){rcub}{dollar} is quenched and is negative at low magnetic fields which depend on the size and the strength of the modulation. (v) For the strong dot potential, there are Aharanov-Bohm oscillations in {dollar}\rm\rho\sbsp{lcub}xx{rcub}{lcub}(0){rcub}{dollar} and {dollar}\rm\rho\sbsp{lcub}xy{rcub}{lcub}(0){rcub}{dollar} and large plus-to-minus oscillations.;The double peak structure in {dollar}\rm\rho\sbsp{lcub}xx{rcub}{lcub}(0){rcub}{dollar} and the negative values and quenching of the Hall effect at low magnetic fields have been observed experimentally for AD in both the quasiclassical and quantum regimes.;In 1D modulation, all the QMT coefficients of a 2DEG in a perpendicular magnetic field for the Short Quantum Wire are calculated in the low magnetic field region ({dollar}<{dollar}0.3 T) using the Kubo method. The Quantum Wire Channel is modulated by controlling the steepness and its strength of the potential barrier. Our studies show a step-like feature in transverse conductivities due to the Landau Level (LL) crossing for the weak modulation and low-field giant peaks in the transverse resistivities for the strong potential. And also, quenched Hall resistivities at low magnetic fields are presented. In longitudinal resistivities, some threshold peaks are shown. Our interesting feature is the negative Hall resistivities which are guessed as the result of the boundary back-scattering in the short Quantum Wire.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
