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Quantized Topological Magnetoelectric Effect Of The Zero Plateau Quantum Anomalous Hall State
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Book Synopsis Quantized Topological Magnetoelectric Effect of the Zero-plateau Quantum Anomalous Hall State by :
Download or read book Quantized Topological Magnetoelectric Effect of the Zero-plateau Quantum Anomalous Hall State written by and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The topological magnetoelectric effect in a three-dimensional topological insulator is a novel phenomenon, where an electric field induces a magnetic field in the same direction, with a universal coefficient of proportionality quantized in units of $e2/2h$. Here in this paper, we propose that the topological magnetoelectric effect can be realized in the zero-plateau quantum anomalous Hall state of magnetic topological insulators or a ferromagnet-topological insulator heterostructure. The finite-size effect is also studied numerically, where the magnetoelectric coefficient is shown to converge to a quantized value when the thickness of the topological insulator film increases. We further propose a device setup to eliminate nontopological contributions from the side surface.
Book Synopsis Quantum Hybrid Electronics and Materials by : Yoshiro Hirayama
Download or read book Quantum Hybrid Electronics and Materials written by Yoshiro Hirayama and published by Springer Nature. This book was released on 2022-05-03 with total page 347 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book highlights recent advances in quantum control technologies with regard to hybrid quantum systems. It addresses the following topics: phonon engineering based on phononic crystals, carbon-based nano materials like graphene and nanotubes, Terahertz light technology for single-molecule and quantum dots, nuclear-spin-based metrology for semiconductor quantum systems, quantum anomalous Hall effect in magnetic topological insulators, chiral three-dimensional photonic crystals, and bio-inspired magnonic systems. Each topic, as a component in the framework of hybrid quantum systems, is concisely presented by experts at the forefront of the field. Accordingly, the book offers a valuable asset, and will help readers find advanced technologies and materials suitable for their purposes.
Book Synopsis Memorial Volume For Shoucheng Zhang by : Xiaoliang Qi
Download or read book Memorial Volume For Shoucheng Zhang written by Xiaoliang Qi and published by World Scientific. This book was released on 2021-08-24 with total page 510 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book honors the remarkable science and life of Shoucheng Zhang, a condensed matter theorist known for his work on topological insulators, the quantum Hall effect, spintronics, superconductivity, and other fields. It contains the contributions displayed at the Shoucheng Zhang Memorial Workshop held on May 2-4, 2019 at Stanford University.
Book Synopsis Topological Insulator and Related Topics by :
Download or read book Topological Insulator and Related Topics written by and published by Academic Press. This book was released on 2021-09-24 with total page 240 pages. Available in PDF, EPUB and Kindle. Book excerpt: Topological Insulator and Related Topics, Volume 108 in the Semiconductors and Semimental series, highlights new advances in the field, with this new volume presenting interesting chapters on topics such as Majorana modes at the ends of one dimensional topological superconductors, Optical/electronic properties of Weyl semimetals, High magnetic fields to unveil the electronic structure, magnetic field-induced transitions, and unconventional transport properties of topological semimetals, New aspects of strongly correlated superconductivity in the nearly flat-band regime, Anomalous transport properties in topological semimetals, Pseudo-gauge field and piezo-electromagnetic response in topological materials, Topological Gapped States Protected by Spatial Symmetries, and more. Provides the authority and expertise of leading contributors from an international board of authors Presents the latest release in the Semiconductors and Semimetals series Updated release includes the latest information on Topological Insulator and Related Topics
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 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 Lithium-Ion Batteries and Solar Cells by : Ming-Fa Lin
Download or read book Lithium-Ion Batteries and Solar Cells written by Ming-Fa Lin and published by CRC Press. This book was released on 2021-01-20 with total page 325 pages. Available in PDF, EPUB and Kindle. Book excerpt: Lithium-Ion Batteries and Solar Cells: Physical, Chemical, and Materials Properties presents a thorough investigation of diverse physical, chemical, and materials properties and special functionalities of lithium-ion batteries and solar cells. It covers theoretical simulations and high-resolution experimental measurements that promote a full understanding of the basic science to develop excellent device performance. Employs first-principles and the machine learning method to fully explore the rich and unique phenomena of cathode, anode, and electrolyte (solid and liquid states) in lithium-ion batteries Develops distinct experimental methods and techniques to enhance the performance of lithium-ion batteries and solar cells Reviews syntheses, fabrication, and measurements Discusses open issues, challenges, and potential commercial applications This book is aimed at materials scientists, chemical engineers, and electrical engineers developing enhanced batteries and solar cells for peak performance.
Book Synopsis Metal-to-insulator Switching in Quantum Anomalous Hall States by :
Download or read book Metal-to-insulator Switching in Quantum Anomalous Hall States written by and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: After decades of searching for the dissipationless transport in the absence of any external magnetic field, quantum anomalous Hall effect (QAHE) was recently achieved in magnetic topological insulator films. However, the universal phase diagram of QAHE and its relation with quantum Hall effect (QHE) remain to be investigated. Here, we report the experimental observation of the giant longitudinal resistance peak and zero Hall conductance plateau at the coercive field in the six quintuple-layer (Cr0.12Bi0.26Sb0.62)2Te3 film, and demonstrate the metal-to-insulator switching between two opposite QAHE plateau states up to 0.3 K. Moreover, the universal QAHE phase diagram is confirmed through the angle-dependent measurements. Our results address that the quantum phase transitions in both QAHE and QHE regimes are in the same universality class, yet the microscopic details are different. Additionally, the realization of the QAHE insulating state unveils new ways to explore quantum phase-related physics and applications.
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 Exploring the Three-dimensional Quantum Anomalous Hall Effect and Topological Superconductivity in Topological Insulator Heterostructures by : Ruoxi Zhang
Download or read book Exploring the Three-dimensional Quantum Anomalous Hall Effect and Topological Superconductivity in Topological Insulator Heterostructures written by Ruoxi Zhang and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Topological materials exhibit unique properties that make them robust against local defects and perturbations. These properties stem from the distinctive band structure compared to conventional materials, which are characterized by different topological invariants. In this thesis, we study two phenomena that arise in epitaxial topological insulator (TIs) films/heterostructures. The first phenomenon is the quantum anomalous Hall (QAH) effect. The QAH effect requires no external magnetic field and possesses non-dissipative chiral edge states that are resistant to local disorders. The second phenomenon is the topological superconducting (TSC) states. The TSC state hosts quasiparticle excitations, including Majorana zero modes (MZMs) and chiral Majorana edge modes (CMEMs). These excitations have potential applications in fault-tolerant topological quantum computations. The first experimental observation of the QAH effect was realized in molecular beam epitaxy (MBE)-grown magnetically doped TI thin films, which offer the advantages of scalability and reproducibility. However, the introduction of magnetic dopants also leads to higher disorder density in TI thin films. To overcome this limitation, we employed MBE-grown magnetically doped TI/TI/magnetically doped TI sandwich heterostructures to separate the magnetic dopants from the TI bulk. By employing this method, we successfully realized high Chern number QAH states, Chern domain walls, and hundred-nanometer-thick QAH samples. These results reveal new phases of matter and the underlying physics of the QAH phase transition induced by interlayer coupling. The second half of the thesis describes our effort in the TSC state in QAH insulators and TIs with induced superconductivity. The first project in this effort focuses on the search for CMEMs, which are predicted to emerge in QAH/superconductor hybrid structures. We examined a prior transport experiment that claimed the realization of CMEMs by measuring the two-terminal resistance. We improved the experimental design by fabricating Josephson junction and tunneling junction devices based on Bi2Te3 and (Bi,Sb)2Te3, and obtained transport results that suggest the dominance of Dirac surface states in vortex generation in the junction area.
Book Synopsis EXPLORATION OF HIGH CHERN NUMBER AND HIGH TEMPERATURE QUANTUM ANOMALOUS HALL EFFECT. by : Yifan Zhao
Download or read book EXPLORATION OF HIGH CHERN NUMBER AND HIGH TEMPERATURE QUANTUM ANOMALOUS HALL EFFECT. written by Yifan Zhao and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Charge-based semiconductor devices are the building blocks of modern electronics. Current flowing through a semiconductor inevitably incurs energy dissipation, the management of which is a key challenge for circuit miniaturization. The search for alternative paradigms of electronics and alternative electronic degrees of freedom, such as spin, is a vibrant frontier in condensed matter physics. Electrons can travel without resistance in a superconductor by forming Cooper pairs; this phenomenon enables the powerful magnets used in magnetic resonance imaging. Wider deployment, however, is limited by the lack of a room-temperature superconductor. Dissipation-free transport can also occur in a two-dimensional "topological insulator (TI)", a material in which the interior is insulating but electrons can travel with less resistance along one-dimensional conducting channels known as edge states [1,2]. A quantum Hall (QH) insulator formed by a sheet of electrons in a strong magnetic field (Nobel Prize in Physics, 1985, 1998) [3] is a special TI material in which edge state current can propagate clockwise or counter-clockwise with zero resistance even at room temperature [4]. The need for an external magnetic field, however, hampers the development of energy-efficient technologies based on the ballistic transport of QH edge states. The necessity of an external magnetic field can be circumvented by exploiting the internal magnetization of a ferromagnet. The possibility of a QH effect at zero magnetic field, now known as the "quantum anomalous Hall (QAH) effect", was envisioned by Haldane in 1988 [5] and first realized experimentally by Chang et al. in 2013 [6]. The QAH effect possesses a quantized Hall resistance of h/Ce2 with spin-polarized dissipation-free chiral edge channels at zero magnetic field, where C, known as the Chern number, corresponds to the number of chiral edge channels. The resistance-free chiral edge channels of the QAH state have been predicted to have potential applications for the exploration of Majorana physics and the next generation of spintronic and electronic devices with low-power consumption. This dissertation focuses on the molecular beam epitaxy (MBE) growth, characterization, and electrical transport measurements of the magnetic TI and QAH insulators, intending to explore the QAH effect with higher Chern numbers and higher critical temperatures. The first topic we addressed is the realization of the high Chern number QAH effect (Chapter 3). The QAH effect has been realized in magnetic TI and twisted moiré material systems. However, the QAH effect in these systems was limited to the Chern number C = 1. In other words, there is only one chiral edge channel in QAH insulators. In C = 1 QAH insulators, the chiral edge current is dissipationless, but the contact resistance between the normal metal electrodes and the chiral edge channels still exists. This contact resistance constrains even proof-of-concept devices that take use of the chiral edge channel transport at zero magnetic field. Here we used MBE to grow magnetic TI/TI multilayer heterostructures and realized the QAH effect with the Chern number from 1 to 5. We further demonstrated the Chern number of the QAH insulators can be tuned by varying either the Cr doping concentration or the thickness of the middle magnetic TI layer. A theoretical model was developed to explain our experimental results. Since the Chern number can be tuned by changing the Cr doping level, the magnetic TI multilayer sample provides us a platform to study the zero magnetic field Chern number change-induced quantum phase transition in QAH insulators. Here, we fabricated the magnetic TI penta-layer heterostructures with different Cr doping concentrations and observed a plateau phase transition between the C = 1 to C = 2 QAH insulators under zero magnetic field (Chapter 4). We demonstrated that the original chiral edge channel from the C = 1 QAH state coexists with the dissipative bulk conduction channels. Subsequently, these bulk conduction channels self-organize and form the second chiral edge channel in completing the plateau phase transition. To explore the proof-of-concept application of the magnetic TI multilayers, we also used the MBE to construct the QAH insulator junctions (Chapter 5), in which two QAH insulators with different Chern numbers were connected along a 1D junction. We observed quantized transport and demonstrated the appearance of the two parallel propagating chiral edge states/ chiral interface channels along the boundary between C = 1 and C = -1 QAH insulators and one single chiral edge state/ chiral interface channel along the boundary between C = 1 to C = 2 insulators. In addition to the magnetically doped TI, we also used MBE to grow the films of intrinsic magnetic TI MnBi2Te4 down to 1 septuple layer (SL) and performed the systematic transport measurements on these films (Chapter 6). We observed a non-square hysteresis loop in the antiferromagnetic state for films with thickness greater than 2 SL. This non-square hysteresis loop can be separated into two AH components and shown to originate from two coexisting phases in the MBE-grown MnBi2Te4 films. One is from the dominant MnBi2Te4 phase with a larger coercive field; the other is from a minor Mn-doped Bi2Te3 phase with a smaller coercive field. The extracted AH component of the MnBi2Te4 phase shows a clear even-odd layer-dependent behavior, a signature of antiferromagnetic thin films. This study reveals insights on how to optimize the MBE growth conditions to improve the quality of MnBi2Te4 films, in which the QAH and other exotic states are predicted.
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.
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 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 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.
Book Synopsis The Universe in a Helium Droplet by : G. E. Volovik
Download or read book The Universe in a Helium Droplet written by G. E. Volovik and published by Oxford University Press on Demand. This book was released on 2003-03-06 with total page 534 pages. Available in PDF, EPUB and Kindle. Book excerpt: This text presents a general overview of analogies between phenomena in condensed matter physics and quantum field theory and elementary particle physics.
Book Synopsis Topology in Magnetism by : Jiadong Zang
Download or read book Topology in Magnetism written by Jiadong Zang and published by Springer. This book was released on 2018-09-24 with total page 426 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents both experimental and theoretical aspects of topology in magnetism. It first discusses how the topology in real space is relevant for a variety of magnetic spin structures, including domain walls, vortices, skyrmions, and dynamic excitations, and then focuses on the phenomena that are driven by distinct topology in reciprocal momentum space, such as anomalous and spin Hall effects, topological insulators, and Weyl semimetals. Lastly, it examines how topology influences dynamic phenomena and excitations (such as spin waves, magnons, localized dynamic solitons, and Majorana fermions). The book also shows how these developments promise to lead the transformative revolution of information technology.
