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Quest For High Temperature And Functional Quantum Anomalous Hall States
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Book Synopsis Quest for High Temperature and Functional Quantum Anomalous Hall States by : Lei Pan
Download or read book Quest for High Temperature and Functional Quantum Anomalous Hall States written by Lei Pan and published by . This book was released on 2019 with total page 138 pages. Available in PDF, EPUB and Kindle. Book excerpt: Quantum anomalous Hall effect (QAHE) is the zero-field version of the quantum Hall effect which shows dissipationless chiral edge electron transport and quantized Hall resistance without the help of external magnetic field. In this Dissertation, we study the growth of magnetic topological insulator (MTI) Cr-doped (BiSb)2Te3 thin film, which is the host of the QAH states, using molecular beam epitaxy. We report the first observation of QAHE in a milli-meter sized device with the thin film thickness beyond the two-dimension (2D) limit. In addition, by controlling the thin film thickness down to the 2D limit, we observe a metal-to-insulator transition behavior due to the hybridization effect introduced by the vertical quantum confinement. We further investigate the temperature limiting factors of QAHE in the Cr-doped (BiSb)2Te3 system by studying the thickness and doping effects. We identify that for thin film thickness larger than 6 quintuple layers (QLs), the limiting factor is the overlap of Fermi level with the trivial bulk band. For thin film thickness equal to 6 QLs, weak ferromagnetism and pronounced superparamagnetism are the temperature limiting factors. However, modulation doping technique can significantly strengthen the ferromagnetism at this thickness. In addition, the metal-to-insulator transition behavior can also be tuned according to the doping profile of the thin film which can potentially affect the phase transition behavior in this material system. To manipulate the QAH states, we investigate the heterogenous integration of the QAH insulator or TI with antiferromagnets. We first study the QAH insulator/Cr2O3 bilayer structure and realize the QAHE on a magnetically ordered system for the first time. We identify the positive exchange bias in this structure and discover the magnetic coupling between the two material systems using polarized neutron reflectometry (PNR). We then study the undoped TI/CrSe heterostructure and realize the antiferromagnet induced magnetic proximity effect in the TI layer confirmed by both PNR and X-ray magnetic dichroism techniques. We also discover the interface-dependent proximity behavior in the heterostructure that may help our understanding towards high temperature and functional QAH states.
Book Synopsis Journal of Research of the National Bureau of Standards by : United States. National Bureau of Standards
Download or read book Journal of Research of the National Bureau of Standards written by United States. National Bureau of Standards and published by . This book was released on 1985 with total page 614 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Visualizing Quantum Anomalous Hall States at the Atomic Scale with STM Landau Level Spectroscopy by : Yi Xue Chong
Download or read book Visualizing Quantum Anomalous Hall States at the Atomic Scale with STM Landau Level Spectroscopy written by Yi Xue Chong and published by . This book was released on 2020 with total page 124 pages. Available in PDF, EPUB and Kindle. Book excerpt: The integer quantum Hall effect (IQH) demonstrates the robust quantization of longitudinal conductance of a 2D electron gas under a strong magnetic field. The theoretically predicted quantum anomalous Hall effect (QAH), which is the IQH counterpart with ferromagnetism taking the role of an external magnetic field, was experimentally demonstrated in 2013 in Cr doped (Bi_xSb_x)_2Te_3 (BST). However, the onset temperature (30 mK) is 2 orders of magnitude lower than the characteristic ferromagnetic critical temperature. The picture often used to describe QAH is this: a 2D topological surface state (SS) exists between the bulk conduction and valence bands. A Dirac mass gap opens when magnetic dopants e.g. Cr are added to create ferromagnetism. Due to its topological nature, a chiral edge state appears when the Fermi level is tuned into the mass gap. Using millikelvin visualization of SS Landau levels, we probe the spatial heterogeneity of the electronic structure due to Sb and Bi intercalation in both BST and CBST, hence discovering that Bi atoms cause a strong shift in the SS Dirac point which is independent of the disordered mass gap caused by the Cr atoms. In consequence, the electrostatic disorder randomizing the Dirac energy and magnetic disorder independently randomizing the Dirac mass gap conspire to drastically suppress the minimum energy gap into the range below 100 micro-eV for nanoscale regions separated by less than a micron. Thus our study reveals what fundamentally limits the fully quantized anomalous Hall effect in Sb2Te3-based ferromagnetic topological insulator (FMTI) materials to very low temperatures.
Download or read book NBS Special Publication written by and published by . This book was released on 1968 with total page 456 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Spintronics written by Claudia Felser and published by Springer Science & Business Media. This book was released on 2013-03-20 with total page 379 pages. Available in PDF, EPUB and Kindle. Book excerpt: Spintronics is an emerging technology exploiting the spin degree of freedom and has proved to be very promising for new types of fast electronic devices. Amongst the anticipated advantages of spintronics technologies, researchers have identified the non-volatile storage of data with high density and low energy consumption as particularly relevant. This monograph examines the concept of half-metallic compounds perspectives to obtain novel solutions and discusses several oxides such as perovskites, double perovskites and CrO2 as well as Heusler compounds. Such materials can be designed and made with high spin polarization and, especially in the case of Heusler compounds, many material-related problems present in current-day 3d metal systems, can be overcome. Spintronics: From Materials to Devices provides an insight into the current research on Heusler compounds and offers a general understanding of structure–property relationships, including the influence of disorder and correlations on the electronic structure and interfaces. Spintronics devices such as magnetic tunnel junctions (MTJs) and giant magnetoresistance (GMR) devices, with current perpendicular to the plane, in which Co2 based Heusler compounds are used as new electrode materials, are also introduced. From materials design by theoretical methods and the preparation and properties of the materials to the production of thin films and devices, this monograph represents a valuable guide to both novices and experts in the fields of Chemistry, Physics, and Materials Science.
Book Synopsis Publications of the National Institute of Standards and Technology ... Catalog by : National Institute of Standards and Technology (U.S.)
Download or read book Publications of the National Institute of Standards and Technology ... Catalog written by National Institute of Standards and Technology (U.S.) and published by . This book was released on 1985 with total page 452 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis The Quantum Hall Effect by : Richard E. Prange
Download or read book The Quantum Hall Effect written by Richard E. Prange and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 487 pages. Available in PDF, EPUB and Kindle. Book excerpt: After a foreword by Klaus von Klitzing, the first chapters of this book discuss the prehistory and the theoretical basis as well as the implications of the discovery of the Quantum Hall effect on superconductivity, superfluidity, and metrology, including experimentation. The second half of this volume is concerned with the theory of and experiments on the many body problem posed by fractional effect. Specific unsolved problems are mentioned throughout the book and a summary is made in the final chapter. The quantum Hall effect was discovered on about the hundredth anniversary of Hall's original work, and the finding was announced in 1980 by von Klitzing, Dorda and Pepper. Klaus von KIitzing was awarded the 1985 Nobel prize in physics for this discovery.
Book Synopsis Publications of the National Bureau of Standards ... Catalog by : United States. National Bureau of Standards
Download or read book Publications of the National Bureau of Standards ... Catalog written by United States. National Bureau of Standards and published by . This book was released on 1984 with total page 450 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Advances in Quantum Anomalous Hall Effect by : Chaolun Wu
Download or read book Advances in Quantum Anomalous Hall Effect written by Chaolun Wu and published by . This book was released on 2020-03 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Magnetic Oscillations in Metals by : D. Shoenberg
Download or read book Magnetic Oscillations in Metals written by D. Shoenberg and published by Cambridge University Press. This book was released on 2009-09-03 with total page 596 pages. Available in PDF, EPUB and Kindle. Book excerpt: It is just over 80 years ago that a striking oscillatory field dependence was discovered in the magnetic behaviour of bismuth at low temperatures. This book was first published in 1984 and gives a systematic account of the nature of the oscillations, of the experimental techniques for their study and of their connection with the electronic structure of the metal concerned. Although the main emphasis is on the oscillations themselves and their many peculiarities, rather than on the theory of the electronic structure they reveal, sufficient examples are given in detail to illustrate the kind of information that has been obtained and how this information agrees with theoretical prediction.
Author :National Academies of Sciences, Engineering, and Medicine Publisher :National Academies Press ISBN 13 :030967882X Total Pages :61 pages Book Rating :4.3/5 (96 download)
Book Synopsis Assessment of the Physical Sciences Directorate at the Army Research Office by : National Academies of Sciences, Engineering, and Medicine
Download or read book Assessment of the Physical Sciences Directorate at the Army Research Office written by National Academies of Sciences, Engineering, and Medicine and published by National Academies Press. This book was released on 2020-07-17 with total page 61 pages. Available in PDF, EPUB and Kindle. Book excerpt: This report summarizes the 2019 findings of the Panel on Review of Extramural Basic Research at the Army Research Laboratory, which reviewed the programs at the Army Research Office's Physical Sciences Directorate.
Book Synopsis Quantum Anomalous Hall Effect in Magnetic Topological Insulators by :
Download or read book Quantum Anomalous Hall Effect in Magnetic Topological Insulators written by and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The search for topologically non-trivial states of matter has become an important goal for condensed matter physics. Here, we give a theoretical introduction to the quantum anomalous Hall (QAH) effect based on magnetic topological insulators in two-dimensions (2D) and three-dimensions (3D). In 2D topological insulators, magnetic order breaks the symmetry between the counter-propagating helical edge states, and as a result, the quantum spin Hall effect can evolve into the QAH effect. In 3D, magnetic order opens up a gap for the topological surface states, and chiral edge state has been predicted to exist on the magnetic domain walls. We present the phase diagram in thin films of a magnetic topological insulator and review the basic mechanism of ferromagnetic order in magnetically doped topological insulators. We also review the recent experimental observation of the QAH effect. Furthermore, we discuss more recent theoretical work on the coexistence of the helical and chiral edge states, multi-channel chiral edge states, the theory of the plateau transition, and the thickness dependence in the QAH effect.
Book Synopsis Quantum Magnetism by : Bernard Barbara
Download or read book Quantum Magnetism written by Bernard Barbara and published by Springer Science & Business Media. This book was released on 2008-06-24 with total page 258 pages. Available in PDF, EPUB and Kindle. Book excerpt: This bookis based on some of the lectures duringthe Paci?c Institute of Theoretical Physics (PITP) summer school on “Quantum Magnetism”, held during June 2006 in Les Houches, in the French Alps. The school was funded jointly by NATO, the CNRS, and PITP, and entirely organized by PITP. Magnetism is a somewhat peculiar research ?eld. It clearly has a quant- mechanical basis – the microscopic exchange interactions arise entirely from the exclusion principle, in conjunction with repulsive interactions between electrons. And yet until recently the vast majority of magnetism researchersand users of m- netic phenomena around the world paid no attention to these quantum-mechanical roots. Thus, e.g., the huge ($400 billion per annum) industry which manufactures hard discs, and other components in the information technology sector, depends entirely on room-temperature properties of magnets – yet at the macroscopic or mesoscopic scales of interest to this industry, room-temperature magnets behave entirely classically.
Book Synopsis Berry Phases in Electronic Structure Theory by : David Vanderbilt
Download or read book Berry Phases in Electronic Structure Theory written by David Vanderbilt and published by Cambridge University Press. This book was released on 2018-11-01 with total page 395 pages. Available in PDF, EPUB and Kindle. Book excerpt: Over the past twenty-five years, mathematical concepts associated with geometric phases have come to occupy a central place in our modern understanding of the physics of electrons in solids. These 'Berry phases' describe the global phase acquired by a quantum state as the Hamiltonian is changed. Beginning at an elementary level, this book provides a pedagogical introduction to the important role of Berry phases and curvatures, and outlines their great influence upon many key properties of electrons in solids, including electric polarization, anomalous Hall conductivity, and the nature of the topological insulating state. It focuses on drawing connections between physical concepts and provides a solid framework for their integration, enabling researchers and students to explore and develop links to related fields. Computational examples and exercises throughout provide an added dimension to the book, giving readers the opportunity to explore the central concepts in a practical and engaging way.
Book Synopsis Science by : John Michels (Journalist)
Download or read book Science written by John Michels (Journalist) and published by . This book was released on 2009 with total page 904 pages. Available in PDF, EPUB and Kindle. Book excerpt: Since Jan. 1901 the official proceedings and most of the papers of the American Association for the Advancement of Science have been included in Science.
Book Synopsis Scientific Papers of Ettore Majorana by : Luisa Cifarelli
Download or read book Scientific Papers of Ettore Majorana written by Luisa Cifarelli and published by Springer Nature. This book was released on 2020-04-28 with total page 192 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents in full the work of the Italian theoretical physicist Ettore Majorana and explains its impacts, which are still being felt. It opens with a contribution by A. Zichichi that considers in depth the scientific genius of Majorana. This introductory chapter is followed, in chronological order, by the eleven scientific papers by this great scientist, in most cases translated into English for the first time. Each paper is accompanied by a comment from an expert in the field in question. Although very few in number, Majorana's papers constitute a heritage of undeniable value and extraordinary scientific meaning, since they laid the foundations for research fields that remain topical today. With this in mind, two additional contributions on ongoing developments in these research fields are included: one on neutrino physics and the other on Majorana fermions in condensed matter. The volume closes with a note on Majorana's life until his ill-fated disappearance.
Download or read book Energy Research Abstracts written by and published by . This book was released on 1984 with total page 816 pages. Available in PDF, EPUB and Kindle. Book excerpt:
