Study of a Two-dimensional Electron Gas in a Magnetic Field PDF Download
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Author: Seung-Joo Lee
Publisher:
ISBN:
Category :
Languages : en
Pages : 162
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Author: Seung-Joo Lee
Publisher:
ISBN:
Category :
Languages : en
Pages : 162
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Author: Tadashi Toyoda
Publisher:
ISBN:
Category :
Languages : en
Pages : 106
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Author: J.T. Devreese
Publisher: Springer Science & Business Media
ISBN: 1461319072
Category : Science
Languages : en
Pages : 444
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Book Description
The 1986 Advanced Study Institute on "The Physics of the two-Dimen sional Electron Gas" took place at the Conference Centre liTer Helme", close to Oostende (Belgium), from June 2 till 16, 1986. We were motivated to organize this Advanced Study Institute in view of the recent experimental and theoretical progress in the study of the two-dimensional electron gas. An additional motivation was our own theore tical interest in cyclotron resonance in two-dimensional electron systems at our institute. It is my pleasure to thank several instances and people who made this Advanced Study Institute possible. First of all, the sponsor of the Advanced Study Institute, the NATO Scientific Committee. Furthermore, the co sponsors: Agfa Gevaert, Bell Telephone Mfg. Co. N.V., Burroughs Belgium. Control Data. Digital Equipment Corporation, Esso Belgium. European Research Office (USA). Kredietbank. National Science Foundation (USA). Special thanks are due to the members of the Program Committee and the members of the Organizing Committee. I would also like to thank Mrs. H. Evans for typing assistance.
Author: M. A. Brummell
Publisher:
ISBN:
Category : Magnetic fields
Languages : en
Pages : 504
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Author: Quoc M. Doan
Publisher:
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Category :
Languages : en
Pages :
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ABSTRACT: We have studied the nematic state of the two dimensional electron gas (2DEG) at halffilled Landau level (LL). Our motivation comes from experiments in which anisotropic transport in the 2DEG under high magnetic field and at low temperature was observed. Based on a model of the nematic state proposed by Oganesyan, Fradkin and Kivelson, we investigate this state and compare it with other competing states proposed by other groups. First, we investigate at what LL the nematic state becomes energetically favorable as compared to the isotropic state. Our studies indicate that this occurs at the second excited LL. Moreover, we compare the energy of the nematic state with that of the stripe state obtained within the Hartree-Fock approximation (HF) and we conclude that, for the samples studied experimentally, the nematic state might be more stable. In our study we have used two different methods which both have advantages and disadvantages.
Author: Hidetoshi Fukuyama
Publisher:
ISBN:
Category :
Languages : en
Pages : 33
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Author: Girish Bohra
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Category :
Languages : en
Pages : 59
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This thesis is focused on an experimental study of the electrical properties of a two-dimensional electron gas formed in a GaAs/AlGaAs heterostructure. Low temperature magneto-transport measurements are used to characterize the carrier density and mobility of this system. An extensive study of the temperature and current dependence of quantum-mechanical transport effects, observable at very low temperatures, is performed in the temperature range of 4.2-100 K, for measurement currents in the range of 10 nA- 100℗æA. The well-known decrease in the amplitude of the Shubnikov-de Haas effect, and an accompanying increase in the onset magnetic field of these oscillations, with increasing temperature, as well as a simultaneous suppression of the quantum-Hall effect, is observed. Similar behavior is found on increasing the measurement current. An analysis of the insulator to quantum Hall transition (I-QH), occurring in the two-dimensional electron gas at low perpendicular magnetic fields, is also reported, along with the results of investigations of electron heating based on the measurements of the energy-loss rate. This study shows that the direct I-QH transition does not always correspond to the onset of strong localization, with clear Shubnikov-de Haas oscillations being observed in the insulating regime. A linear dependence of the electron energy-loss rate and electron temperature in the temperature range of 4.2-40 K is determined, indicating that the main mechanism for electron energy relaxation is acoustic phonon scattering.
Author: E.Y. Andrei
Publisher: Springer Science & Business Media
ISBN: 9401512868
Category : Science
Languages : en
Pages : 398
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Book Description
Recent studies on two-dimensional systems have led to new insights into the fascinating interplay between physical properties and dimensionality. Many of these ideas have emerged from work on electrons bound to the surface of a weakly polarizable substrate such as liquid helium or solid hydrogen. The research on this subject continues to be at the forefront of modern condensed matter physics because of its fundamental simplicity as well as its connection to technologically useful devices. This book is the first comprehensive overview of experimental and theoretical research in this exciting field. It is intended to provide a coherent introduction for graduate students and non-experts, while at the same time serving as a reference source for active researchers in the field. The chapters are written by individuals who made significant contributions and cover a variety of specialized topics. These include the origin of the surface states, tunneling and magneto-tunneling out of these states, the phase diagram, collective excitations, transport and magneto-transport.
Author: Jeremy A. Curtis
Publisher:
ISBN:
Category : Cyclotrons
Languages : en
Pages : 55
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This dissertation covers two projects that were in the logical path to studying decoherence in a high mobility GaAs two-dimensional electron gas at high magnetic fields. The first project is the ultrafast non-degenerate pump-probe spectroscopic study of bulk GaAs in the Split Florida Helix at the National High Magnetic Field Laboratory at Florida State University. This project was undertaken as a proof of concept that ultrafast optics could be done in the Split Florida Helix so that we might study a high mobility two dimensional electron gas using THz time-domain spectroscopy at high magnetic fields, which is a much more complicated measurement than the pump-probe discussed here. This demonstration was a success. We completed the first ultrafast optical study of any kind in the Florida Split Helix. We collected differential reflection data from this bulk sample that exhibited electronic and oscillatory components. These components were treated independently in the analysis by treating the electronic dynamics with a four level approximation. The electronic transition rates were extracted and agreed well with published values. This agreement is a demonstration that the spectrometer functioned as desired. The oscillatory response was found to be a result of the emission of coherent phonons upon electronic transition between the four levels. The frequency of the oscillatory response was extracted and agreed well with the theoretical value. The second project is the study of the temperature dependence of the cyclotron decay lifetimes in a Landau quantized GaAs high mobility two dimensional electron gas using THz time-domain spectroscopy at relatively low magnetic field (1.25 T). We find that the cyclotron decay lifetimes decrease monotonically with increasing temperature from 0.4 K to 100 K and that the primary pulse amplitudes increase from 0.4 K to 1.2 K, saturates above 1.2 K up to 50 K, and decreases rapidly above 50 K. We attribute this rapid drop in amplitude above 50 K as well as the high temperature behavior of the cyclotron resonance decay times to polar optical phonon scattering. We find that the dissipative component of the measured cyclotron decay lifetimes can not be well approximated by a DC scattering lifetime model, which includes polar optical phonon scattering, remote ionized impurity scattering, acoustic deformation potential scattering, and piezo-electric scattering. This discrepancy is due to the entirely different distribution of the Fermi surface resulting from the Landau quantization of the quantum well's states. This project demonstrates the type of measurements we would like to conduct at higher magnetic fields using more broadband THz sources. Future work is finally discussed, which outlines the construction and demonstration of a custom ultra broadband THz time-domain spectrometer for use in the Florida Split Helix. The data collected is not of sufficient quality to extract physical meaning due to its decreased signal to noise and bandwidth relative to the test of the system through the magnet without sample or windows at 0 T and 300 K, which demonstrated the generation and detection of 15 THz of usable bandwidth. This reduction in signal to noise and bandwidth is due to clipping the THz beam on the magnet aperture. Future measurements will use optically clear windows that are also transparent in the THz so that alignment of the THz beam may be done with an optical beam. While the original goal was an extension of the temperature dependent measurements described in the previous paragraph at much higher applied magnetic field strength, the design, construction, and demonstration of the system without sample or windows as well as the data set collected through a high mobility GaAs two dimensional electron gas at 25 T and 15 K constitutes the first THz time-domain measurements conducted in the Florida Split Helix.
Author: L. Ioriatti
Publisher:
ISBN:
Category :
Languages : en
Pages : 10
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The Wigner function of a two-dimensional electron gas in an arbitrary magnetic field perpendicular to the plane in which the electrons are confined in constructed rigorously. The function is useful in taking various statistical averages and illuminates the roles played by the hyperbolic functions of the field which appear in the expressions of the susceptibility and other physical quantities.
