Download or read book Topological Insulators written by Gregory Tkachov and published by CRC Press. This book was released on 2015-10-14 with total page 180 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book is the result of dynamic developments that have occurred in condensed matter physics after the recent discovery of a new class of electronic materials: topological insulators. A topological insulator is a material that behaves as a band insulator in its interior, while acting as a metallic conductor at its surface. The surface current car
Download or read book Quantum Transport in Topological Insulators written by Johannes Krotz and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Quantum Transport in 2 and 3 Dimensional Topological Insulators written by Di Xiao and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Topological insulators are materials that are insulating in the bulk but that conduct via topologically protected states on the boundary. The concept of topology in condensed matter physics was first introduced to explain the integer quantum Hall (IQH) effect. The perfect quantization of these topologically protected edge states, insensitive to sample geometry and disorder, stimulated an extensive search for many exciting new topological materials. One of the milestones along the journey was the theoretical prediction and experimental discovery of Z2 topological insulators.The first class of Z2 topological insulators discovered was the 2-dimensional topological insulator (2D TI), also known as the quantum spin Hall (QSH) insulator. The 2D TI can be viewed as a variation of the IQH system but with time-reversal-symmetry (TRS). The topological invariant for a 2D TI is the Z2 number, defined by its nontrivial band structure instead of the Chern number in the IQH case. Generalizing this idea to 3 dimensions led to the discovery of the 3D TI with four Z2 invariants. Both the 2D and 3D TIs are of interest as model platforms for testing theoretical problems of fundamental interest. For instance, they allow us to realize artificial condensed matter analogs of fundamental particles such as Majorana fermions and axions that have yet to be observed in nature. They are also of interest for potential technological applications, principally spintronics and quantum computing.This dissertation focuses on the synthesis, characterization, and transport properties of both 2D and 3D TIs. We first discuss the 2D TI candidate material system, type II InAs/GaSb quantum wells, which exhibits a rich topological phase diagram that can be tuned by several parameters such as sample geometry or electrostatic gating. By changing the thicknesses of relevant layers, we are able to enter a new insulating regime where unexpected high-density quantum oscillations are observed. We elucidate this phenomenon through theoretical calculation and through control experiments. The seemingly controversial coexistence of high density states and the insulating regime can be explained by the effect of the attractive Coulomb interaction, which was not considered in earlier theories.The second topic we address is quantum transport in 3D TI systems. Breaking the TRS of the 3D TI surface states leads to many exotic phenomena, including the quantum anomalous Hall (QAH) effect and the axion insulator state. By constructing a sandwich heterostructure that has different magnetic coercive fields in the top and bottom magnetic layers, while keeping the center layer free from magnetic impurities, both the QAH and the axion insulator state can be observed in low-temperature transport measurements, when the magnetization alignment of the top and bottom layers is parallel and antiparallel, respectively. We also discuss the scaling behavior of the topological quantum phase transition between these two states.
Download or read book Quantum Transport in Magnetic Topological Insulators written by Shu-Wei Wang and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Quantum Transport in Topological Nanostructures written by Emily Elizabeth and published by . This book was released on 2023-10-27 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Quantum Transport Through Graphene and Topological Insulators written by Nuno José Guimarães Couto and published by . This book was released on 2014 with total page 122 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Quantum Transport Study in 3D Topological Insulators Nanostructures written by Louis Veyrat and published by . This book was released on 2016* with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book QUANTUM TRANSPORT IN TOPOLOGICAL MATERIALS written by Run Xiao and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation focuses on the synthesis, characterization, fabrication, and electrical transport measurements of topological materials, including magnetically doped topological insulators and Dirac semimetal Cd3As2. Bismuth-chalcogenide topological insulators have time-reversal-symmetry-protected surface states due to the strong spin-orbit coupling. Breaking the time-reversal symmetry by magnetic dopants can lead to fascinating exotic phenomena, such as the quantum anomalous Hall effect. On the other hand, Dirac semimetals host three-dimensional Dirac fermions and can be identified as a parent phase of other topological phases, such as Weyl semimetals. In this dissertation, quantum transport measurements are performed on thin films of topological materials to investigate and understand the unusual electronic states that host these topological phases. These studies can motivate and facilitate the development of potential applications of topological materials, especially in spintronics and quantum computing. The first topological material studied in this dissertation is a magnetically doped topological insulator system: Cr doped (Bi,Sb)2Te3 - (Bi,Sb)2Te3 - Cr doped (Bi,Sb)2Te3 sandwich heterostructure. By tuning the chemical and asymmetric potentials using dual gates, both the quantum anomalous hall effect, due to the topology in the momentum space, and the topological Hall effect, due to the topology in real space, can be observed in this heterostructure system. We also mapped out a phase diagram of the topological Hall and quantum anomalous Hall effects as a function of the chemical and asymmetry potentials, paving a way to understand and manipulate the chiral magnetic spin textures in real space. The second topological material is Dirac semimetal Cd3As2. We investigated the integer quantum Hall effect in Cd3As2 thin films under strong to moderate quantum confinement (thicknesses of 10 nm, 12 nm, and 15 nm). In all the films, we observed the integer quantum Hall effect in the spin-polarized lowest Landau level (filling factor [nu]=1) and at spin-degenerate higher index Landau levels with even filling factors ([nu]=2,4,6). We also observed the lifting of the Landau level spin degeneracy at v=3 with strong quantum confinement. A tight-binding calculation suggests that the enhanced g-factor due to the quantum confinement and corrections from nearby subbands can be the reason for the emergence of v=3 quantum Hall plateau. Last, we explored the introduction of the transition metal Mn into Cd3As2 thin films to break the time-reversal symmetry. Scanning transmission electron microscopy of these films shows a formation of an Mn-rich layer on top of a pure Cd3As2 layer using both uniform and delta doping methods. The low solubility of Mn in Cd3As2 can be the reason for the phase separation. The Mn-rich region shows out-of-plane magnetic anisotropy in superconducting quantum interference device magnetometry measurements. Moreover, the presence of the Mn surfactant lowers the carrier density in the Cd3As2 layer, and an incipient quantum Hall effect can be observed in low-temperature transport measurements.
Download or read book Quantum Transport in 2D Topological Insulator Device written by 李欣翰 and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Numerical Studies of Quantum Transport in Topological Insulator Nanowire Superconductor Junctions written by Michael Barth and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Quantum Transport in HgTe Topological Insulator Nanostructures written by Johannes Ziegler and published by . This book was released on 2018 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book An Introduction to Quantum Transport in Semiconductors written by David K. Ferry and published by CRC Press. This book was released on 2017-12-14 with total page 323 pages. Available in PDF, EPUB and Kindle. Book excerpt: Throughout their college career, most engineering students have done problems and studies that are basically situated in the classical world. Some may have taken quantum mechanics as their chosen field of study. This book moves beyond the basics to highlight the full quantum mechanical nature of the transport of carriers through nanoelectronic structures. The book is unique in that addresses quantum transport only in the materials that are of interest to microelectronics—semiconductors, with their variable densities and effective masses. The author develops Green’s functions starting from equilibrium Green’s functions and going through modern time-dependent approaches to non-equilibrium Green’s functions, introduces relativistic bands for graphene and topological insulators and discusses the quantum transport changes that these bands induce, and discusses applications such as weak localization and phase breaking processes, resonant tunneling diodes, single-electron tunneling, and entanglement. Furthermore, he also explains modern ensemble Monte Carlo approaches to simulation of various approaches to quantum transport and the hydrodynamic approaches to quantum transport. All in all, the book describes all approaches to quantum transport in semiconductors, thus becoming an essential textbook for advanced graduate students in electrical engineering or physics.
Download or read book Exploration of Quantum Transport Phenomena via Engineering Emergent Magnetic Fields in Topological Magnets written by Yukako Fujishiro and published by Springer. This book was released on 2022-12-03 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book addresses novel electronic and thermoelectronic properties arising from topological spin textures as well as topologically non-trivial electronic structures. In particular, it focuses on a unique topological spin texture, i.e., spin hedgehog lattice, emerging in a chiral magnet and explore its novel properties which are distinct from the conventional skyrmion lattice, and discusses the possibility of realizing high-temperature quantum anomalous Hall effect through quantum confinement effect in topological semimetal. This book benefits students and researchers working in the field of condensed matter physics, through providing comprehensive understanding of the current status and the outlook in the field of topological magnets.
Download or read book Topological Insulators written by C. Brüne and published by Elsevier Inc. Chapters. This book was released on 2013-11-23 with total page 27 pages. Available in PDF, EPUB and Kindle. Book excerpt: This chapter will focus on the experimental properties of the quantum spin Hall effect in HgTe quantum well structures. HgTe quantum wells above a critical thickness are 2-dimensional topological insulators. The most prominent signature of the non-trivial topology in these systems is the occurrence of the quantum spin Hall effect when the Fermi energy is located inside the bulk band gap. We will present the main experimental results we obtained for transport in the quantum spin Hall regime and discuss how they confirm the prediction of the quantum spin Hall effect as a helical edge state system consisting of two counterpropagating oppositely spin polarized edge states.
Download or read book Quantum Transport in Topological Phases of Matter written by Michal Papaj and published by . This book was released on 2021 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Topological phases of matter attract constant attention in the condensed matter physics community, both due to the fundamental yet simple principles that govern them, and a multitude of experimental observations with the potential for technological applications. Among the ways of studying such materials, quantum transport methods prove to be of particular importance. In this thesis, I touch upon many aspects of quantum transport in topological materials. First, I introduce a novel type of Hall effect, called Magnus Hall effect, that allows one to probe Berry curvature in ballistic, time-reversal invariant systems that break inversion symmetry. Next, I present a detailed characterization of extrinsic Nernst effect in Dirac and Weyl semimetals, providing interpretation of existing experimental results and predictions for new enhanced responses in materials such as Fe3Sn2. In the following section, I demonstrate that a strong disorder can lead to a novel behavior of Dirac fermions in surface states of topological crystalline insulators, resulting in appearance of nodal arcs in place of Dirac points and in tilting of the Dirac cone. In the second part of the thesis, I focus on topological superconductors, starting by presenting a new method for creating Majorana zero modes using segmented Fermi surface. This approach, based on the Fermi surface of Bogoliubov quasiparticles allows for the reduction of the magnetic field required to induce a topological phase transition and reduces the number of spurious, low energy modes that hamper observation and utilization of Majorana zero modes. Finally, I show that the presence of multiple Majorana modes in a strongly correlated superconducting island leads to Kondo-like behavior with a topological twist.
Download or read book Topological Insulators written by Vadim Nemytov and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: "In this thesis we investigate quantum transport properties of topological insulator (TI) Bi2 Se3 from atomistic point of view. TI is a material having an energy gap in its bulk but supporting gapless helical states on its boundary. The helical states have Dirac-like linear energy dispersion continuously crossing the bulk band gap with a spin texture in which the electron spin is locked perpendicular to the electron momentum. The peculiar electronic structure of TI material Bi2 Se3 is due to a strong spin-orbit interaction and is protected by the time reversal symmetry. The thesis consists of two main parts. The first reviews the theory of TI and the second presents our atomistic calculations of electron transport in the Bi2 Se3 material. In the theoretical review of the physics of TI, I follow the literature and attempt to present it in a reasonably accessible manner. The theory of TI is explained in terms of well known physical phenomena including classical and quantum Hall effects, spin-orbit coupling, spin current, and spin-Hall effect. The concept of Berry's phase is then introduced to link with the formal conventionalclassification of TI by the topological Z2 invariants. The entire discussion is within the well known Bloch band theory. In the second part of this thesis, numerical studies of transport properties of Bi2 Se3 are presented. After a brief discussion of the relevant quantum transport theory and the tight binding atomistic model, we present our calculated quantum transport results of Bi2 Se3 films having a trench in the middle. Such a large defect, if on normal conductors, would cause significant back scattering of the carriers. Here, by topological protection of the helical states, back scattering is forbidden due to the spin-momentum locking. Nevertheless, large trenches in the film may cause the helical states on the surface to mix inside the trench, thereby affecting the transmission." --
Download or read book Quantum Transport Theory of 3D Time reversal Invariant Topological Insulators written by and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
