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Quantum Anomalous Hall Effect In Hg 1 Ymn Yte Quantum Wells
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Book Synopsis Quantum Anomalous Hall Effect in Hg_1-yMn_yTe Quantum Wells by :
Download or read book Quantum Anomalous Hall Effect in Hg_1-yMn_yTe Quantum Wells written by and published by . This book was released on 2010 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt: The quantum Hall effect is usually observed when the two-dimensional electron gas is subjected to an external magnetic field, so that their quantum states form Landau levels. In this work we predict that a new phenomenon, the quantum anomalous Hall effect, can be realized in Hg{sub 1-y}Mn{sub y}Te quantum wells, without the external magnetic field and the associated Landau levels. This effect arises purely from the spin polarization of the Mn atoms, and the quantized Hall conductance is predicted for a range of quantum well thickness and the concentration of the Mn atoms. This effect enables dissipationless charge current in spintronics devices.
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 Topological Quantum Materials by : Grigory Tkachov
Download or read book Topological Quantum Materials written by Grigory Tkachov and published by CRC Press. This book was released on 2022-08-18 with total page 288 pages. Available in PDF, EPUB and Kindle. Book excerpt: In topological quantum materials, quantum effects emerge at macroscopic scales and are robust to continuous changes in a material’s state. This striking synergy between quantum and topological properties is of great interest for both fundamental research and emerging technologies, especially in the fields of electronics and quantum information. This edition of the book presents a wealth of topological quantum materials, bringing together burgeoning research from different areas: topological insulators, transition metal dichalcogenides, Weyl semimetals, and unconventional and topological superconductors. The realization of the application potential of topological quantum materials requires understanding their properties at a fundamental level. This brings us back to the discovery of topological phases of matter, which earned the Nobel Prize in Physics in 2016. This book explores the connection between pioneering work on topological phases of matter and a flurry of activity that followed. The topics covered include the quantum anomalous and spin Hall effects, emergent axion electrodynamics and topological magnetoelectric effects, Weyl nodes and surface Fermi arcs, weak antilocalization, induced triplet superconductivity, Majorana fermion modes, and the fractional Josephson effect.
Book Synopsis Quantum Anomalous Hall Effects by : Heiner Denker
Download or read book Quantum Anomalous Hall Effects written by Heiner Denker and published by . This book was released on 2018-02 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis The Fractional Quantum Hall Effect by : Tapash Chakraborty
Download or read book The Fractional Quantum Hall Effect written by Tapash Chakraborty and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 186 pages. Available in PDF, EPUB and Kindle. Book excerpt: The experimental discovery of the fractional quantum Hall effect (FQHE) at the end of 1981 by Tsui, Stormer and Gossard was absolutely unexpected since, at this time, no theoretical work existed that could predict new struc tures in the magnetotransport coefficients under conditions representing the extreme quantum limit. It is more than thirty years since investigations of bulk semiconductors in very strong magnetic fields were begun. Under these conditions, only the lowest Landau level is occupied and the theory predicted a monotonic variation of the resistivity with increasing magnetic field, depending sensitively on the scattering mechanism. However, the ex perimental data could not be analyzed accurately since magnetic freeze-out effects and the transitions from a degenerate to a nondegenerate system complicated the interpretation of the data. For a two-dimensional electron gas, where the positive background charge is well separated from the two dimensional system, magnetic freeze-out effects are barely visible and an analysis of the data in the extreme quantum limit seems to be easier. First measurements in this magnetic field region on silicon field-effect transistors were not successful because the disorder in these devices was so large that all electrons in the lowest Landau level were localized. Consequently, models of a spin glass and finally of a Wigner solid were developed and much effort was put into developing the technology for improving the quality of semi conductor materials and devices, especially in the field of two-dimensional electron systems.
Book Synopsis The Quantum Hall Effect by : Daijiro Yoshioka
Download or read book The Quantum Hall Effect written by Daijiro Yoshioka and published by Springer Science & Business Media. This book was released on 2013-03-09 with total page 214 pages. Available in PDF, EPUB and Kindle. Book excerpt: The fractional quantum Hall effect has opened up a new paradigm in the study of strongly correlated electrons and it has been shown that new concepts, such as fractional statistics, anyon, chiral Luttinger liquid and composite particles, are realized in two-dimensional electron systems. This book explains the quantum Hall effects together with these new concepts starting from elementary quantum mechanics.
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 Fractional Quantum Hall Effect in Wide Quantum Wells by : Javad Shabani
Download or read book Fractional Quantum Hall Effect in Wide Quantum Wells written by Javad Shabani and published by . This book was released on 2011 with total page 268 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 433 pages. Available in PDF, EPUB and Kindle. Book excerpt: analyze the Hall effect in the plateau region relative to the fundamental value 2 h/e i expected in the simple one-electron picture for integer filling factors of Landau levels. Subsequent work in my laboratory in Wiirzburg using a super conducting solenoid confirmed the constancy of the Hall resistance both in Dorda's samples and in samples supplied by M. Pepper of the Cavendish Laboratory. With technical assistance from the Physikalisch-Technische Bundesanstalt in Braunschweig, an absolute measurement of the Hall resistance confirmed the 2 fundamental quantization relation RIJ = h/ei to an accuracy of about 1 part in ]05. Recalling the practical applications of the Josephson effect, my initial thinking was oriented toward the idea of a resistance standard, but various groups at national laboratories which are involved in high precision measurements of fun damental constants pointed out that, in addition, the quantized Hall resistance yields a new fundamental measure of the fine structure constant Ci. These then were the initial events which led to the remarkable surge of interest within both the metrology and condensed matter physics communities in quantum transport in inversion layer systems. Subsequent developments have been many and varied and are described in detail in this volume.
Download or read book The Quantum Spin Hall Effect written by and published by . This book was released on 2010 with total page 32 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. Recently, a new class of topological insulators has been proposed. These topological insulators have an insulating gap in the bulk, but have topologically protected edge states due to the time reversal symmetry. In two dimensions the helical edge states give rise to the quantum spin Hall (QSH) effect, in the absence of any external magnetic field. Here we review a recent theory which predicts that the QSH state can be realized in HgTe/CdTe semiconductor quantum wells. By varying the thickness of the quantum well, the band structure changes from a normal to an 'inverted' type at a critical thickness d{sub c}. We present an analytical solution of the helical edge states and explicitly demonstrate their topological stability. We also review the recent experimental observation of the QSH state in HgTe/(Hg, Cd)Te quantum wells. We review both the fabrication of the sample and the experimental setup. For thin quantum wells with well width d{sub QW} 6.3 nm, the insulating regime shows the conventional behavior of vanishingly small conductance at low temperature. However, for thicker quantum wells (d{sub QW} 6.3 nm), the nominally insulating regime shows a plateau of residual conductance close to 2e2/h. The residual conductance is independent of the sample width, indicating that it is caused by edge states. Furthermore, the residual conductance is destroyed by a small external magnetic field. The quantum phase transition at the critical thickness, d{sub c} = 6.3 nm, is also independently determined from the occurrence of a magnetic field induced insulator to metal transition.
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 The Quantum Hall Effect by : Richard E. Prange
Download or read book The Quantum Hall Effect written by Richard E. Prange and published by . This book was released on 1990 with total page 473 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Unexpected Edge Conduction in Mercury Telluride Quantum Wells Under Broken Time-reversal Symmetry by :
Download or read book Unexpected Edge Conduction in Mercury Telluride Quantum Wells Under Broken Time-reversal Symmetry written by and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The realization of quantum spin Hall effect in HgTe quantum wells is considered a milestone in the discovery of topological insulators. Quantum spin Hall states are predicted to allow current flow at the edges of an insulating bulk, as demonstrated in various experiments. A key prediction yet to be experimentally verified is the breakdown of the edge conduction under broken time-reversal symmetry. Here we first establish a systematic framework for the magnetic field dependence of electrostatically gated quantum spin Hall devices. We then study edge conduction of an inverted quantum well device under broken time-reversal symmetry using microwave impedance microscopy, and compare our findings to a non-inverted device. At zero magnetic field, only the inverted device shows clear edge conduction in its local conductivity profile, consistent with theory. Surprisingly, the edge conduction persists up to 9 T with little change. Finally, this indicates physics beyond simple quantum spin Hall model, including material-specific properties and possibly many-body effects.
Book Synopsis Intrinsic Quantum Anomalous Hall Effect in the Kagome Lattice Cs2LiMn3F12 by :
Download or read book Intrinsic Quantum Anomalous Hall Effect in the Kagome Lattice Cs2LiMn3F12 written by and published by . This book was released on 2016 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Quantized Hall Effect in Single Quantum Wells of InAs by : E. E. Mendez
Download or read book Quantized Hall Effect in Single Quantum Wells of InAs written by E. E. Mendez and published by . This book was released on 1984 with total page 7 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Topological Insulators and Topological Superconductors by : B. Andrei Bernevig
Download or read book Topological Insulators and Topological Superconductors written by B. Andrei Bernevig and published by Princeton University Press. This book was released on 2013-04-07 with total page 264 pages. Available in PDF, EPUB and Kindle. Book excerpt: This graduate-level textbook is the first pedagogical synthesis of the field of topological insulators and superconductors, one of the most exciting areas of research in condensed matter physics. Presenting the latest developments, while providing all the calculations necessary for a self-contained and complete description of the discipline, it is ideal for graduate students and researchers preparing to work in this area, and it will be an essential reference both within and outside the classroom. The book begins with simple concepts such as Berry phases, Dirac fermions, Hall conductance and its link to topology, and the Hofstadter problem of lattice electrons in a magnetic field. It moves on to explain topological phases of matter such as Chern insulators, two- and three-dimensional topological insulators, and Majorana p-wave wires. Additionally, the book covers zero modes on vortices in topological superconductors, time-reversal topological superconductors, and topological responses/field theory and topological indices. The book also analyzes recent topics in condensed matter theory and concludes by surveying active subfields of research such as insulators with point-group symmetries and the stability of topological semimetals. Problems at the end of each chapter offer opportunities to test knowledge and engage with frontier research issues. Topological Insulators and Topological Superconductors will provide graduate students and researchers with the physical understanding and mathematical tools needed to embark on research in this rapidly evolving field.
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.
