Theory of Transport Properties of Semiconductor Nanostructures


Book Description

Recent advances in the fabrication of semiconductors have created almost un limited possibilities to design structures on a nanometre scale with extraordinary electronic and optoelectronic properties. The theoretical understanding of elec trical transport in such nanostructures is of utmost importance for future device applications. This represents a challenging issue of today's basic research since it requires advanced theoretical techniques to cope with the quantum limit of charge transport, ultrafast carrier dynamics and strongly nonlinear high-field ef fects. This book, which appears in the electronic materials series, presents an over view of the theoretical background and recent developments in the theory of electrical transport in semiconductor nanostructures. It contains 11 chapters which are written by experts in their fields. Starting with a tutorial introduction to the subject in Chapter 1, it proceeds to present different approaches to transport theory. The semiclassical Boltzmann transport equation is in the centre of the next three chapters. Hydrodynamic moment equations (Chapter 2), Monte Carlo techniques (Chapter 3) and the cellular au tomaton approach (Chapter 4) are introduced and illustrated with applications to nanometre structures and device simulation. A full quantum-transport theory covering the Kubo formalism and nonequilibrium Green's functions (Chapter 5) as well as the density matrix theory (Chapter 6) is then presented.




Electrical Transport in Nanoscale Systems


Book Description

In recent years there has been a huge increase in the research and development of nanoscale science and technology. Central to the understanding of the properties of nanoscale structures is the modeling of electronic conduction through these systems. This graduate textbook provides an in-depth description of the transport phenomena relevant to systems of nanoscale dimensions. In this textbook the different theoretical approaches are critically discussed, with emphasis on their basic assumptions and approximations. The book also covers information content in the measurement of currents, the role of initial conditions in establishing a steady state, and the modern use of density-functional theory. Topics are introduced by simple physical arguments, with particular attention to the non-equilibrium statistical nature of electrical conduction, and followed by a detailed formal derivation. This textbook is ideal for graduate students in physics, chemistry, and electrical engineering.




Electrical Conduction in Graphene and Nanotubes


Book Description

Written in a self-contained manner, this textbook allows both advanced students and practicing applied physicists and engineers to learn the relevant aspects from the bottom up. All logical steps are laid out without omitting steps. The book covers electrical transport properties in carbon based materials by dealing with statistical mechanics of carbon nanotubes and graphene - presenting many fresh and sometimes provoking views. Both second quantization and superconductivity are covered and discussed thoroughly. An extensive list of references is given in the end of each chapter, while derivations and proofs of specific equations are discussed in the appendix. The experienced authors have studied the electrical transport in carbon nanotubes and graphene for several years, and have contributed relevantly to the understanding and further development of the field. The content is based on the material taught by one of the authors, Prof Fujita, for courses in quantum theory of solids and quantum statistical mechanics at the University at Buffalo, and some topics have also been taught by Prof. Suzuki in a course on advanced condensed matter physics at the Tokyo University of Science. For graduate students in physics, chemistry, electrical engineering and material sciences, with a knowledge of dynamics, quantum mechanics, electromagnetism and solid-state physics at the senior undergraduate level. Includes a large numbers of exercise-type problems.




Observation of Superconductivity in Epitaxially Grown Atomic Layers


Book Description

This thesis presents first observations of superconductivity in one- or two-atomic-scale thin layer materials. The thesis begins with a historical overview of superconductivity and the electronic structure of two-dimensional materials, and mentions that these key ingredients lead to the possibility of the two-dimensional superconductor with high phase-transition temperature and critical magnetic field. Thereafter, the thesis moves its focus onto the implemented experiments, in which mainly two different materials thallium-deposited silicon surfaces and metal-intercalated bilayer graphenes, are used. The study of the first material is the first experimental demonstration of both a gigantic Rashba effect and superconductivity in the materials supposed to be superconductors without spatial inversion symmetry. The study of the latter material is relevant to superconductivity in a bilayer graphene, which was a big experimental challenge for a decade, and has been first achieved by the author. The description of the generic and innovative measurement technique, highly effective in probing electric resistivity of ultra-thin materials unstable in an ambient environment, makes this thesis a valuable source for researchers not only in surface physics but also in nano-materials science and other condensed-matter physics.







Functional Nanostructures and Metamaterials for Superconducting Spintronics


Book Description

This book demonstrates how the new phenomena in the nanometer scale serve as the basis for the invention and development of novel nanoelectronic devices and how they are used for engineering nanostructures and metamaterials with unusual properties. It discusses topics such as superconducting spin-valve effect and thermal spin transport, which are important for developing spintronics; fabrication of nanostructures from antagonistic materials like ferromagnets and superconductors, which lead to a novel non-conventional FFLO-superconducting state; calculations of functional nanostructures with an exotic triplet superconductivity, which are the basis for novel nanoelectronic devices, such as superconducting spin valve, thin-film superconducting quantum interference devices (SQUIDs) and memory-elements (MRAM). Starting with theoretical chapters about triplet superconductivity, the book then introduces new ideas and approaches in the fundamentals of superconducting electronics. It presents various quantum devices based on the new theoretical approaches, demonstrating the enormous potential of the electronics of 21st century - spintronics. The book is useful for a broad audience, including researchers, engineers, PhD graduates, students and others wanting to gain insights into the frontiers of nanoscience.




Transport Properties of Chiral P-wave Superconductor-normal Metal Nanostructures


Book Description

In this thesis, we present a theory of electron transport for unconventional superconductors. We focus on the superconducting properties of Sr2RuO4, which is a strong candidate for two dimensional p-wave superconductivity in electronic systems. We present Green function formulation of the theory of superconductivity and reduce the formulation within quasiclassical approximation. To study the systems with disordered normal metal junctions, we derive the boundary conditions of quasiclassical equations from the microscopic theory considering a spin active boundary. Boundary between normal metal and superconductor is modeled with Rashba type spin orbit coupling. An exact solution of the resulting equations are given and the resistance of the model system is calculated as a function of temperature, boundary transparency and superconducting state symmetry. The developed theory is used to study the phase transition of unconventional superconductors with increasing impurity concentration. It has been shown that, in the strong disordered regime, system can be modeled as Mattis model known from the theory of spin glasses. We show that with increasing disorder there will be two consecutive phase transitions: A phase transition from unconventional superconductor to s-wave superconductor followed by a transition from s-wave superconductor to normal metal. A qualitative phase diagram is prsented and corrections to Mattis model approximation is considered.




Superconductivity in Nanowires


Book Description

The importance and actuality of nanotechnology is unabated and will be for years to come. A main challenge is to understand the various properties of certain nanostructures, and how to generate structures with specific properties for use in actual applications in Electrical Engineering and Medicine. One of the most important structures are nanowires, in particular superconducting ones. They are highly promising for future electronics, transporting current without resistance and at scales of a few nanometers. To fabricate wires to certain defined standards however, is a major challenge, and so is the investigation and understanding of these properties in the first place. A promising approach is to use carbon nanotubes as well as DNA structures as templates. Many fundamental theoretical questions are still unanswered, e.g. related to the role of quantum fluctuations. This work is tackling them and provides a detailed analysis of the transport properties of such ultrathin wires. It presents an account of theoretical models, charge transport experiments, and also conveys the latest experimental findings regarding fabrication, measurements, and theoretical analysis. In particular, it is the only available resource for the approach of using DNA and carbon nanotubes for nanowire fabrication. It is intended for graduate students and young researchers interested in nanoscale superconductivity. The readers are assumed to have knowledge of the basics of quantum mechanics and superconductivity.




Semiconductor Nanostructures


Book Description

This introduction to the physics of semiconductor nanostructures and their transport properties emphasizes five fundamental transport phenomena: quantized conductance, tunnelling transport, the Aharonov-Bohm effect, the quantum Hall effect and the Coulomb blockade effect.