Emerging Phenomena in Two-dimensional Electron System in Intermediate Magnetic Fields PDF Download

Author: Sanghun An
Publisher:
ISBN:
Category :
Languages : en
Pages :

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Abstract: The interlayer electron-electron interaction in bilayer two-dimensional electron system has been studied in tilted magnetic fields through electron drag measurements. In intermediate magnetic fields, where the temperature of electrons is comparable or larger than Landau level spacing, electrons near Fermi level can access more than one Landau level and inter-Landau level scatterings play an important role in transport properties of the system. In such a regime, we observed that the resonant 2k_F interlayer phonon exchange present in perpendicular magnetic fields is suppressed by moderate in-plane magnetic fields. Furthermore, in the absence of such resonant phonon exchange, the magneto-enhancement of drag is nearly temperature-independent and has a highly unusual B_perp^3 field dependence. We argue that the drastic suppression of 2k_F phonon exchange in tilted magnetic fields might be related to the substantial change in out-of-plane Lorentz force on electrons by in-plane component of fields during the 2k_F scattering process. We also argue that highly unusual temperature and field dependences of drag in tilted magnetic fields might be a consequence of fully-activated inter-Landau level scatterings, which are often neglected.

Author: Israel D. Vagner
Publisher: Springer Science & Business Media
ISBN: 9401002215
Category : Science
Languages : en
Pages : 343

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A comprehensive collection of papers on theoretical aspects of electronic processes in simple and synthetic metals, superconductors, bulk and low-dimensional semiconductors under extreme conditions, such as high magnetic and electric fields, low and ultra-low temperatures. The main emphasis is on low-dimensional conductors and superconductors, where correlated electrons, interacting with magnetic or nonmagnetic impurities, phonons, photons, or nuclear spins, result in a variety of new physical phenomena, such as quantum oscillations in the superconducting state, Condon instability, Skyrmions and composite fermions in quantum Hall effect systems, and hyperfine field-induced mesoscopic and nanoscopic phenomena. Several new experimental achievements are reported that promise to delineate future trends in low temperature and high magnetic field physics, including the experimental observation of the interplay between superconductivity and nuclear spin ordering at ultra-low temperatures, new observations of Condon domains in normal metals, and an experimental proposal for the realisation of isotopically engineered, semiconductor-based spin-qubit elements for future quantum computation and communication technology.

Author: E.Y. Andrei
Publisher: Springer Science & Business Media
ISBN: 9401512868
Category : Science
Languages : en
Pages : 398

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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: Meng Ma
Publisher:
ISBN:
Category :
Languages : en
Pages : 0

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Electron and hole systems confined in two dimensions exhibit a plethora of exotic quantum phases under perpendicular magnetic field at sufficiently low temperature. In this thesis, we explore several of these quantum phases in state-of-the-art high-quality InAs and GaAs quantum wells and study their formation, phase diagram, and geometric resonance behavior under a one-dimensional periodic magnetic modulation.The two-dimensional (2D) electron system in an InAs quantum well has emerged as a prime candidate for hosting exotic quasi-particles with non-abelian statistics such as Majorana fermions and parafermions. To attain its full promise, however, the electron system has to be clean enough to exhibit electron-electron interaction phenomena. In the first part of the thesis, we present the observation of the fractional quantum Hall effect in a very low disorder InAs quantum well. At sufficiently low temperature and very high perpendicular magnetic field, a deep minimum in the longitudinal resistance, accompanied by a nearly quantized Hall plateau at Landau level filling factor nu=4/3 was observed.A sufficiently large perpendicular magnetic field quenches the kinetic (Fermi) energy of an interacting 2D system of fermions, making them susceptible to the formation of a Wigner solid (WS) phase in which the charged carriers organize themselves in a periodic array to minimize their Coulomb repulsion energy. In low-disorder 2D electron systems confined to modulation-doped GaAs heterostructures, signatures of a magnetic-field-induced WS appear at low temperatures and very small Landau level filling factors (nu~1/5). In dilute GaAs 2D hole systems, on the other hand, thanks to the larger hole effective mass and the ensuing Landau level mixing, the WS forms at relatively higher fillings (nu~1/3). In the second part of the thesis, we present our measurements of the fundamental temperature vs. filling phase diagram for the 2D holes' WS-liquid thermal melting. Moreover, via changing the 2D hole density, we also probe their Landau level mixing vs. filling WS-liquid quantum melting phase diagram. We find our data to be in good agreement with the results of very recent calculations, although intriguing subtleties remain.A high-quality 2D electron system under a small perpendicular magnetic field exhibits ballistic cyclotron motion. When the size of the cyclotron orbit is commensurate with an external one-dimensional (1D) density modulation, a series of longitudinal resistance minima are observed as a result of this geometric resonance condition. In a GaAs 2D electron system, such 1D density modulation can be achieved through the piezoelectric effect along the [110] and [-110] crystallographic directions. In the third part of this thesis, we discuss a technique that imposes a 1D magnetic modulation to the GaAs 2D electron system in the [100] and [010] crystallographic directions where the piezoelectric effect essentially zero. This technique can be implemented to study the geometric resonance of other 2D systems such as the AlAs 2D electron system, where the major axes of the carrier pockets are along the directions. By extending this technique to higher perpendicular magnetic fields, one can also add an additional tool to probe the physics of the composite fermion systems.

Author: Eva Pavarini
Publisher: Forschungszentrum Jülich
ISBN: 3893368841
Category :
Languages : en
Pages : 562

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Author: National Research Council
Publisher: National Academies Press
ISBN: 0309095824
Category : Science
Languages : en
Pages : 189

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High-field magnetsâ€"those that operate at the limits of the mechanical and/or electromagnetic properties of their structural materialsâ€"are used as research tools in a variety of scientific disciplines. The study of high magnetic fields themselves is also important in many areas such as astrophysics. Because of their importance in scientific research and the possibility of new breakthroughs, the National Science Foundation asked the National Research Council to assess the current state of and future prospects for high-field science and technology in the United States. This report presents the results of that assessment. It focuses on scientific and technological challenges and opportunities, and not on specific program activities. The report provides findings and recommendations about important research directions, the relative strength of U.S. efforts compared to other countries, and ways in which the program can operate more effectively.

Author: National Research Council
Publisher: National Academies Press
ISBN: 0309286379
Category : Science
Languages : en
Pages : 233

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The Committee to Assess the Current Status and Future Direction of High Magnetic Field Science in the United States was convened by the National Research Council in response to a request by the National Science Foundation. This report answers three questions: (1) What is the current state of high-field magnet science, engineering, and technology in the United States, and are there any conspicuous needs to be addressed? (2) What are the current science drivers and which scientific opportunities and challenges can be anticipated over the next ten years? (3) What are the principal existing and planned high magnetic field facilities outside of the United States, what roles have U.S. high field magnet development efforts played in developing those facilities, and what potentials exist for further international collaboration in this area? A magnetic field is produced by an electrical current in a metal coil. This current exerts an expansive force on the coil, and a magnetic field is "high" if it challenges the strength and current-carrying capacity of the materials that create the field. Although lower magnetic fields can be achieved using commercially available magnets, research in the highest achievable fields has been, and will continue to be, most often performed in large research centers that possess the materials and systems know-how for forefront research. Only a few high field centers exist around the world; in the United States, the principal center is the National High Magnetic Field Laboratory (NHMFL). High Magnetic Field Science and Its Application in the United States considers continued support for a centralized high-field facility such as NHFML to be the highest priority. This report contains a recommendation for the funding and siting of several new high field nuclear magnetic resonance magnets at user facilities in different regions of the United States. Continued advancement in high-magnetic field science requires substantial investments in magnets with enhanced capabilities. High Magnetic Field Science and Its Application in the United States contains recommendations for the further development of all-superconducting, hybrid, and higher field pulsed magnets that meet ambitious but achievable goals.

Author: H. Aoki
Publisher: Springer Science & Business Media
ISBN: 9401131902
Category : Science
Languages : en
Pages : 471

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In Bird of Passage by Rudolf Peierls, we find a paragraph in which he de scribes his Cambridge days in the 1930s: On these [relativistic field theory] problems my main contacts were Dirac, and the younger theoreticians. These included in particular Nevill (now Sir Nevill) Mott, perhaps the friendliest among many kind and friendly people we met then. Professor Kamimura became associated with Sir Rudolf Peierls in the 1950s, when he translated, with his colleagues, Peierls's 1955 textbook, Quantum Theory of Solids, into Japanese. This edition, to which Sir Rudolf himself contributed a preface, benefitted early generations of Japanese solid state physicists. Later in 1974/5, during a sabbatical year spent at the Cavendish Laboratory, Professor Kamimura met and began a long association with Sir Nevill Mott. In particular, they developed ideas for disordered systems. One of the outcomes is a paper coauthored by them on ESR-induced variable range hopping in doped semiconductors. A series of works on disordered systems, together with those on two-dimensional systems, have served as building blocks for Physics of Interacting Electrons in Disordered Systems, in the International Series of Monographs on Physics, coauthored by Aoki and published in 1989 by the Oxford University Press. Soon after Professor Kamimura obtained a D. Sc. in 1959 for the work on the ligand field theory under the supervision ofMasao Kotani, his strong con nections in the international physical community began when he worked at the Bell Telephone Laboratories in 1961/64.

Author: Fritz Herlach
Publisher: World Scientific
ISBN: 9814490547
Category : Science
Languages : en
Pages : 281

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This three-volume book provides a comprehensive review of experiments in very strong magnetic fields that can only be generated with very special magnets. The first volume is entirely devoted to the technology of laboratory magnets: permanent, superconducting, high-power water-cooled and hybrid; pulsed magnets, both nondestructive and destructive (megagauss fields). Volumes 2 and 3 contain reviews of the different areas of research where strong magnetic fields are an essential research tool. These volumes deal primarily with solid-state physics; other research areas covered are biological systems, chemistry, atomic and molecular physics, nuclear resonance, plasma physics and astrophysics (including QED).

Author: Gottfried Landwehr
Publisher: Springer Science & Business Media
ISBN: 3642838103
Category : Technology & Engineering
Languages : en
Pages : 666

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This volume contains contributions presented at the International Conference "The Application of High Magnetic Fields in Semiconductor Physics", which was held at the University of Wiirzburg from August 22 to 26, 1988. In the tradition of previous Wiirzburg meetings on the subject - the first conference was held in 1972 - only invited papers were presented orally. All 42 lecturers were asked to review their subject to some extent so that this book gives a good overview of the present state of the respective topic. A look at the contents shows that the subjects which have been treated at previous conferences have not lost their relevance. On the contrary, the application of high magnetic fields to semiconductors has grown substantially during the recent past. For the elucidation of the electronic band structure of semicon ductors high magnetic fields are still an indispensable tool. The investigation of two-dimensional electronic systems especially is frequently connected with the use of high magnetic fields. The reason for this is that a high B-field adds angular momentum quantization to the boundary quantization present in het erostructures and superlattices. A glance at the contributions shows that the majority deal with 2D properties. Special emphasis was on the integral and fractional quantum Hall effect. Very recent results related to the observation of a fraction with an even denbminator were presented. It became obvious that the polarization of the different fractional Landau levels is more complicated than originally anticipated.