Exploring the Three-dimensional Quantum Anomalous Hall Effect and Topological Superconductivity in Topological Insulator Heterostructures PDF Download
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Author: Ruoxi Zhang
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
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.
Author: Ruoxi Zhang
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
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.
Author: Joel E. Moore
Publisher: Elsevier Inc. Chapters
ISBN: 0128086831
Category : Science
Languages : en
Pages : 31
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Book Description
The theory of the topological insulator phase that emerges via spin-orbit coupling in three-dimensional materials is introduced, stressing its relationship to earlier topological phases in two dimensions. An unusual surface state with an odd number of “Dirac points” appears as a consequence of bulk topological invariants of the band structure. A different theoretical approach is then presented, based on the Berry phase of Bloch electrons, in order to illustrate a deep connection to the orbital contribution to the magnetoelectric polarizability in all materials. The unique features of transport in the topological insulator surface state are reviewed with an emphasis on possible experiments. The final section discusses briefly connections to interacting phases including topological superconductors and some recent efforts to construct fractional topological insulators in three dimensions.
Author: Inamuddin
Publisher: Materials Research Forum LLC
ISBN: 1644902850
Category : Technology & Engineering
Languages : en
Pages : 195
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Book Description
A topological insulator is an area that has yet to be fully explored and developed. The charge-induced bandgap fluctuation in the best-known bismuth-chalcogenide-based topological insulators is approximately 10MeV in magnitude. The major focus has shifted to the investigation of the presence of high-symmetry electronic bands as well as the utilization of easily produced materials. As the subject of topological insulators is still in the nascent stage, there is growing research and knowledge in the emerging field. This book is intended to provide the readers with an understanding of the needs and application of these materials. Keywords: Topological Insulators, Insulators, One-Dimensional Topological Insulators, Graphene, Magnetic Topological Insulator, Antiferromagnetic Phase, Ferromagnetic Phase, Topological Superconductor, Nonlinear Optical Behavior, Saturable Absorber, Quantum, Band Gap, Photonic Topological Insulators.
Author: Xiao-Liang Qi
Publisher: Elsevier Inc. Chapters
ISBN: 0128086858
Category : Science
Languages : en
Pages : 43
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Book Description
In this chapter we provide an overview of the topological field theory approach to topological insulators. We start by reviewing the topological field theory description of integer quantum Hall states, which also illustrates the general features of topological field theory approach. Then we reviewed the topological field theory approach of three-dimensional topological insulators and its physical consequences. In the last part of this section we discuss the generalizations of topological field theory approach to generic dimensions and other topological states of matter.
Author: Huixia Luo
Publisher: John Wiley & Sons
ISBN: 111940732X
Category : Technology & Engineering
Languages : en
Pages : 400
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Book Description
This book 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 researchers and graduate students preparing to work in this area, and it will be an essential reference both within and outside the classroom. The book begins with the fundamental description on the topological phases of matter such as one, two- and three-dimensional topological insulators, and methods and tools for topological material's investigations, topological insulators for advanced optoelectronic devices, topological superconductors, saturable absorber and in plasmonic devices. Advanced Topological Insulators provides researchers and graduate students with the physical understanding and mathematical tools needed to embark on research in this rapidly evolving field.
Author: Shun-Qing Shen
Publisher: Springer Science & Business Media
ISBN: 364232858X
Category : Technology & Engineering
Languages : en
Pages : 234
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Book Description
Topological insulators are insulating in the bulk, but process metallic states present around its boundary owing to the topological origin of the band structure. The metallic edge or surface states are immune to weak disorder or impurities, and robust against the deformation of the system geometry. This book, the first of its kind on topological insulators, presents a unified description of topological insulators from one to three dimensions based on the modified Dirac equation. A series of solutions of the bound states near the boundary are derived, and the existing conditions of these solutions are described. Topological invariants and their applications to a variety of systems from one-dimensional polyacetalene, to two-dimensional quantum spin Hall effect and p-wave superconductors, and three-dimensional topological insulators and superconductors or superfluids are introduced, helping readers to better understand this fascinating new field. This book is intended for researchers and graduate students working in the field of topological insulators and related areas. Shun-Qing Shen is a Professor at the Department of Physics, the University of Hong Kong, China.
Author: Naoto Nagaosa
Publisher: Elsevier Inc. Chapters
ISBN: 0128086912
Category : Science
Languages : en
Pages : 39
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Book Description
The discovery of the rich topological structures of electronic states in solids has opened up many interesting possibilities. The “twist” of the wavefunctions in momentum space, which is characterized by topological invariants, leads to the robust edge or surface states. The electron fractionalization associated with these topological states brings about the novel physics such as absence of localization, topological magneto-electric effect, and Majorana fermions. Here we describe the principles and some concrete examples of the theoretical design of the topological materials and their functions based on these recent developments.
Author: B. Andrei Bernevig
Publisher: Princeton University Press
ISBN: 069115175X
Category : Science
Languages : en
Pages : 259
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Book Description
"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..."--
Author: Gaurav Chaudhary (Ph. D.)
Publisher:
ISBN:
Category :
Languages : en
Pages : 284
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Book Description
This dissertation presents studies of topological superconductivity in Chern insulator systems. In particular, when a Chern insulator such as a quantum Hall or a quantum anomalous Hall system is proximity coupled to a trivial s-wave superconductor. While quantum anomalous Hall based system is investigated in detail in both one and two dimensions, the focus is solely on two dimensions in quantum Hall bases system. Both quantum Hall and quantum anomalous Hall break time reversal (T)-symmetry. Hence throughout this thesis, we focus on the T-symmetry broken topological superconductor systems, which fall in the class [double struck D] of the Altland-Zirnbauer classification. After a brief introduction to thesis in chapter 1 and review of topological superconductivity in chapter 2, in chapter 3, a realistic system motivated from the experimental observation of the quantum anomalous Hall effect is considered. The focus of this chapter is on one dimensional (1D) topological superconducting phase in thin ribbon geometries [Phys. Rev. B 97, 081102(R)]. It identifies the quantum anomalous Hall based system as highly controllable platform for Majorana zero modes, which can be potentially used as Majorana braiding device. In chapter 4, two dimensional (2D) topological superconducting phase in the quantum Hall based system is studied [arXiv:1903.12249]. Because of the inherent requirement of the external magnetic field to achieve quantum Hall physics, this system requires consideration of vortex lattice phase in the parent superconductor. It is shown that the topological superconducting phase is determined by the type of vortex lattice. Hence, making quantum Hall based system different than quantum anomalous Hall based system, giving much richer phase diagram. Experimental protocol to engineer and observe Majorana edge modes in this system is also discussed. In chapter 5, reentrant superconductivity under magnetic fields beyond semiclassical critical magnetic field is discussed. It is argued that recently discovered superconductivity in magic angle twisted bilayer graphene (MATBG) can be a promising ground to observe this phase. In chapter 6, recent transport experiments in quantum anomalous Hall/superconductor devices are discussed. The two main experiments on this system have contradictory results and there is widespread debate on possible explanations of the experimental observations, which can born out of chiral Majorana mode (i.e. topological) or disorder (i.e. trivial). The main arguments on both sides are summarized and some strategies to resolve the debate are proposed
Author: Jeroen B. Oostinga
Publisher: Elsevier Inc. Chapters
ISBN: 0128086890
Category : Science
Languages : en
Pages : 48
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Book Description
The discovery of topological insulators as a new state of matter has generated immense interest in this new class of materials. Three-dimensional (3D) topological insulators are characterized by the presence of an odd number of families of Dirac fermions—ideally one- at each of their surfaces. Angle-resolved photoemission experiments have demonstrated the presence of the expected Dirac fermions, but it is clear that to explore the electronic properties of these systems, transport measurements in many different device geometries are called for, just as it has been the case for Dirac fermions in graphene. In this chapter we review the status of transport studies through 3D topological insulators as of early summer 2012, after that a first generation of experiments has been performed. The results provide many different indications of the presence of surface fermions, as well as evidence of their Dirac nature. However, no textbook “manifestation” of surface Dirac fermions has been reported so far in these materials. Indeed, experiments also show that investigations are severely hampered by the material quality in most cases, because of the effect of high conductivity in the bulk, of low carrier mobility, of technical difficulties hampering device fabrication, and other reasons. In this chapter, we attempt to give a balanced overview of the work done during this first period and of the results obtained, stressing the implications and the limits of many of the observations that have been reported in the literature.
