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Author: Seung Sae Hong Publisher: ISBN: Category : Languages : en Pages :
Book Description
Topological insulators are states of quantum matter with an insulating gap in the bulk and gapless surface states. The exotic spin nature of the surface electrons, resulting in topological protection from localization, suggests unconventional applications in electronics as well as fundamental scientific interests. While these exotic states have been investigated via surface-sensitive techniques intensively, electronic transport device, crucial to realize topological electronics, has lagged behind due to material challenges in candidate materials. Topological insulator nanostructure is an attractive candidate for device applications, as the size effect and boundary conditions offer a unique way to enhance / tailor the surface electron transport. In this dissertation, we first describe the design principle of topological insulator nanomaterials, with an emphasis on bismuth selenide. Two major material challenges, dominant bulk electron contribution and low surface mobility due to surface oxidation, are discussed and the solutions via nanomaterial synthesis are achieved. Elemental doping and core-shell heterostructures are developed to suppress bulk carriers and to achieve high surface electron mobility. The high electronic mobility allows us to observe Shubnikov-de Haas oscillations originated from the surface Dirac fermions. In addition to the material development, we also investigate transport properties from helical nature of the surface electrons. 1D modes of surface electrons in bismuth selenide nanowire Aharonov-Bohm interferometers is a unique electronic state providing an opportunity to reveal helical spin nature and topological protection via transport. The helical 1D mode, directly observed near the Dirac point under half magnetic flux quantum, is robust against disorder but fragile against a magnetic field breaking time-reversal-symmetry. The newly discovered 1D helical mode is expected to open a new direction to study topological electronics, as well as future applications.
Author: Seung Sae Hong Publisher: ISBN: Category : Languages : en Pages :
Book Description
Topological insulators are states of quantum matter with an insulating gap in the bulk and gapless surface states. The exotic spin nature of the surface electrons, resulting in topological protection from localization, suggests unconventional applications in electronics as well as fundamental scientific interests. While these exotic states have been investigated via surface-sensitive techniques intensively, electronic transport device, crucial to realize topological electronics, has lagged behind due to material challenges in candidate materials. Topological insulator nanostructure is an attractive candidate for device applications, as the size effect and boundary conditions offer a unique way to enhance / tailor the surface electron transport. In this dissertation, we first describe the design principle of topological insulator nanomaterials, with an emphasis on bismuth selenide. Two major material challenges, dominant bulk electron contribution and low surface mobility due to surface oxidation, are discussed and the solutions via nanomaterial synthesis are achieved. Elemental doping and core-shell heterostructures are developed to suppress bulk carriers and to achieve high surface electron mobility. The high electronic mobility allows us to observe Shubnikov-de Haas oscillations originated from the surface Dirac fermions. In addition to the material development, we also investigate transport properties from helical nature of the surface electrons. 1D modes of surface electrons in bismuth selenide nanowire Aharonov-Bohm interferometers is a unique electronic state providing an opportunity to reveal helical spin nature and topological protection via transport. The helical 1D mode, directly observed near the Dirac point under half magnetic flux quantum, is robust against disorder but fragile against a magnetic field breaking time-reversal-symmetry. The newly discovered 1D helical mode is expected to open a new direction to study topological electronics, as well as future applications.
Author: Frank Ortmann Publisher: John Wiley & Sons ISBN: 3527681604 Category : Technology & Engineering Languages : en Pages : 434
Book Description
There are only few discoveries and new technologies in physical sciences that have the potential to dramatically alter and revolutionize our electronic world. Topological insulators are one of them. The present book for the first time provides a full overview and in-depth knowledge about this hot topic in materials science and condensed matter physics. Techniques such as angle-resolved photoemission spectrometry (ARPES), advanced solid-state Nuclear Magnetic Resonance (NMR) or scanning-tunnel microscopy (STM) together with key principles of topological insulators such as spin-locked electronic states, the Dirac point, quantum Hall effects and Majorana fermions are illuminated in individual chapters and are described in a clear and logical form. Written by an international team of experts, many of them directly involved in the very first discovery of topological insulators, the book provides the readers with the knowledge they need to understand the electronic behavior of these unique materials. Being more than a reference work, this book is essential for newcomers and advanced researchers working in the field of topological insulators.
Author: Frank Ortmann Publisher: John Wiley & Sons ISBN: 3527681582 Category : Technology & Engineering Languages : en Pages : 432
Book Description
There are only few discoveries and new technologies in physical sciences that have the potential to dramatically alter and revolutionize our electronic world. Topological insulators are one of them. The present book for the first time provides a full overview and in-depth knowledge about this hot topic in materials science and condensed matter physics. Techniques such as angle-resolved photoemission spectrometry (ARPES), advanced solid-state Nuclear Magnetic Resonance (NMR) or scanning-tunnel microscopy (STM) together with key principles of topological insulators such as spin-locked electronic states, the Dirac point, quantum Hall effects and Majorana fermions are illuminated in individual chapters and are described in a clear and logical form. Written by an international team of experts, many of them directly involved in the very first discovery of topological insulators, the book provides the readers with the knowledge they need to understand the electronic behavior of these unique materials. Being more than a reference work, this book is essential for newcomers and advanced researchers working in the field of topological insulators.
Author: Vadim Nemytov Publisher: ISBN: Category : Languages : en Pages :
Book Description
"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." --
Author: Massimo V. Fischetti Publisher: Springer ISBN: 3319011014 Category : Technology & Engineering Languages : en Pages : 481
Book Description
This textbook is aimed at second-year graduate students in Physics, Electrical Engineering, or Materials Science. It presents a rigorous introduction to electronic transport in solids, especially at the nanometer scale.Understanding electronic transport in solids requires some basic knowledge of Hamiltonian Classical Mechanics, Quantum Mechanics, Condensed Matter Theory, and Statistical Mechanics. Hence, this book discusses those sub-topics which are required to deal with electronic transport in a single, self-contained course. This will be useful for students who intend to work in academia or the nano/ micro-electronics industry.Further topics covered include: the theory of energy bands in crystals, of second quantization and elementary excitations in solids, of the dielectric properties of semiconductors with an emphasis on dielectric screening and coupled interfacial modes, of electron scattering with phonons, plasmons, electrons and photons, of the derivation of transport equations in semiconductors and semiconductor nanostructures somewhat at the quantum level, but mainly at the semi-classical level. The text presents examples relevant to current research, thus not only about Si, but also about III-V compound semiconductors, nanowires, graphene and graphene nanoribbons. In particular, the text gives major emphasis to plane-wave methods applied to the electronic structure of solids, both DFT and empirical pseudopotentials, always paying attention to their effects on electronic transport and its numerical treatment. The core of the text is electronic transport, with ample discussions of the transport equations derived both in the quantum picture (the Liouville-von Neumann equation) and semi-classically (the Boltzmann transport equation, BTE). An advanced chapter, Chapter 18, is strictly related to the ‘tricky’ transition from the time-reversible Liouville-von Neumann equation to the time-irreversible Green’s functions, to the density-matrix formalism and, classically, to the Boltzmann transport equation. Finally, several methods for solving the BTE are also reviewed, including the method of moments, iterative methods, direct matrix inversion, Cellular Automata and Monte Carlo. Four appendices complete the text.
Author: Vasilios N. Stavrou Publisher: BoD – Books on Demand ISBN: 1789234689 Category : Science Languages : en Pages : 130
Book Description
The current book entitled Heterojunctions and Nanostructures is divided into two sections. In Section 1, the chapters are related to topological insulators where their theoretical aspects, their current experiments, and their applications are presented. A few presented topics are, among others, the topological phases of matter, band topology of insulators and also of Weyl semimetals, transport properties of 3D topological insulator quantum wires and the influence of disorder, transport properties of quasi-1D (and 2D) topological surface states, quantum coherence, and topological insulator thin-film Hall bar device. In Section 2, the chapters are related to light devices such as laser diodes and their fabrication techniques. This section includes, among others, topics such as semiconductor quantum nanowire laser diodes, solutions of Schrodinger equation in nanostructures, numerical methods, light-to-electricity conversion devices, photoexcited carrier transportation process in quantum wells and quantum dots, growth mode and characterization of heterostructure of large lattice mismatch, and photoionization cross section.
Author: Seung Sae Hong
Author: Seung Sae Hong
Author: Emily Elizabeth
Author: Frank Ortmann
Author: Frank Ortmann
Author: Vadim Nemytov
Author: Sungjae Cho
Author: Massimo V. Fischetti
Author: Vasilios N. Stavrou
Author: Zhenghe Jin
Author: Sven Essert