Author: Matthew Joel BeneshPublisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
Charge Transport Dynamics of Surface Acoustic Waves in a GaAs
Author: Matthew Joel BeneshElectron Dynamics in Surface Acoustic Wave Devices
Author: Adam Leslie ThornPublisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
Gallium arsenide is piezoelectric, so it is possible to generate coupled mechanical and electrical surface acoustic waves (SAWs) by applying a high-frequency voltage to a transducer on the surface of GaAs. By combining SAWs with existing low-dimensional nanostructures one can create a series of dynamic quantum dots corresponding to the minima of the travelling electric wave, and each dot carries a single electron at the SAW velocity (~ 2800 m/s). These devices may be of use in developing future quantum information processors, and also offer an ideal environment for probing the quantum mechanical behaviour of single electrons. This thesis describes a numerical and theoretical study of the dynamics ofan electron in a range of geometries. The numerical techniques for solving thetime-dependent Schrödinger equation with an arbitrary time-dependent potential will be described in Chapter 2, and then applied in Chapter 3 to calculate the transmission of an electron through an Aharonov-Bohm (AB) ring. It will be seen that an important property of the techniques used in this thesis is that they can be easily adapted to study realistic geometries, and we will see features in the AB oscillations which do not arise in simplified analytic descriptions. In Chapter 4, we will then study a device consisting of two parallel SAW channels separated by a controllable tunnelling barrier. We will use numerical simulations to investigate the effect of electric and magnetic fields upon the electron dynamics, and develop an analytic model to explain the simulation results. From the model, it will be apparent that it is possible to use this device to rotatethe state of the electron to an arbitrary superposition of the first two eigenstates. We then introduce coherent and squeezed states in Chapter 5, which are ex-cited states of the quantum harmonic oscillator. Coherent and squeezed electronicstates may be of use in quantum information processing, and could also arise dueto unwanted perturbations in a SAW device. We will discuss how these statescan be controllably generated in a SAW device, and also discuss how they couldthen be detected. In Chapter 6 we describe how to use the motion of a SAW to create a rapidly-changing potential in the frame of the electron, leading to a nonadiabatic excita-tion. The nonadiabatically-excited state oscillates from side to side within a 1Dchannel on a few-picosecond timescale, and this motion can be probed by placing a tunnelling barrier at one side of the channel. Numerical simulations will beperformed to show how this motion can be controlled, and the simulation resultswill be seen to be in good agreement with recent experimental work performed by colleagues. Finally, we will show that this device can be used to measure the initial state of an electron which is an arbitrary superposition of the first twoeigenstates.
Atomic Scale Dynamics at Surfaces
Author: Giorgio BenedekPublisher: Springer
ISBN: 3662564432
Category : Science
Languages : en
Pages : 625
Book Description
Experimental advances in helium atom scattering spectroscopy over the last forty years have allowed the measurement of surface phonon dispersion curves of more than 200 different crystal surfaces and overlayers of insulators, semiconductors and metals. The first part of the book presents, at a tutorial level, the fundamental concepts and methods in surface lattice dynamics, and the theory of atom-surface interaction and inelastic scattering in their various approximations, up to the recent electron-phonon theory of helium atom scattering from conducting surfaces. The second part of the book, after introducing the experimentalist to He-atom spectrometers and the rich phenomenology of helium atom scattering from corrugated surfaces, illustrates the most significant experimental results on the surface phonon dispersion curves of various classes of insulators, semiconductors, metals, layered crystals, topological insulators, complex surfaces, adsorbates, ultra-thin films and clusters. The great potential of helium atom scattering for the study of atomic scale diffusion, THz surface collective excitations, including acoustic surface plasmons, and the future prospects of helium atom scattering are presented in the concluding chapters. The book will be valuable reading for all researchers and graduate students interested in dynamical processes at surfaces.
Exciton Transport in GaAs/AlGaAs Quantum Wells Using Surface Acoustic Waves
Author: Barbara Lammie WamplerPublisher:
ISBN:
Category : Acoustic surface wave devices
Languages : en
Pages : 102
Book Description
Spin and Charge Ordering in the Quantum Hall Regime
Author: Benedikt FrießPublisher: Springer
ISBN: 3319335367
Category : Computers
Languages : en
Pages : 137
Book Description
The book presents a comprehensive yet concise introduction to the physics of two-dimensional electron systems in the quantum Hall regime, as well as an up-to-date overview of the current fields of research concerning the integer and fractional quantum Hall effect. The physics of two-dimensional electron systems at low temperatures and high magnetic fields are governed by the formation of discrete energy levels referred to as Landau levels. These narrow energy bands not only form the basis of the well-known quantum Hall effect but also promote strong interactions between the electrons, giving rise to some of the finest manifestations of many-body physics in solid state science. Examples include skyrmionic spin textures, ferromagnetic spin transitions, stripe and bubble phases, as well as fractional quantum Hall states with potential non-abelian exchange statistics. The thesis succeeds in profoundly deepening our understanding of these exotic states of matter, with a main focus on the density-modulated phases in the quantum Hall regime. These phases arise from the interplay of competing interactions and are characterized by a self-organized ordering of electrons in spatial patterns. Similar phases of matter are currently being studied in other material systems as well, most notably in high-temperature superconductors. The thesis stands out not only in terms of its contribution to improving readers’ grasp of physics, but also in the diversity and novelty of the measurement techniques employed, which take advantage of the interaction between the electrons and the surrounding crystal lattice.
Creating and Imaging Surface Acoustic Waves on GaAs
Author: Publisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
The versatility of surface acoustic wave (SAW) devices stems from the accessibility of the propagation path to modification and detection. This has led to the integration of SAWs in a variety of novel fields, including quantum information processing. The development of technologically competitive devices requires the use of gigahertz frequency SAWs. This thesis develops fabrication processes for high frequency interdigital transducers on gallium arsenide. Optically lithography was used to create linear and stepped transducers, with a minimum feature size of 2 um, that were driven at their fifth harmonic. The highest frequency achieved was 1435 MHz, but the power absorbed was less than 3% and insertion losses were greater than -80 dB. Further improvements in the design and fabrication are required if optically fabricated transducers are to be an alternative to transducers with narrower finger widths. Electron-beam lithography techniques were developed and used to create transducers with finger widths of 500 and 400 nm, with fundamental resonance frequencies of 1387 and 1744 MHz, respectively. The power absorbed was 3 to 6% with insertion losses greater than -45 dB. The performance characteristics can be improved by the removal of residual resist on the surface of the transducer. An indispensable tool for the characterization of one-port transducers is an all optical probe to measure the displacement field of a SAW. This work details the design and construction of a scanning Sagnac interferometer, that is capable of measuring the outward displacement of a surface. The spatial resolution of the interferometer was 2.4 +/- 0.2 um and the displacement sensitivity was determined to be 4 +/- 1 pm. The instrument was used to map the SAW displacement field from a 358 MHz transducer, with results showing the resonant cavity behaviour of the fingers due to Bragg reflections. It also allowed for the direct detection of the SAW amplitude as a function of the driving frequency of.
Scientific and Technical Aerospace Reports
Author: Epioptics-9 - Proceedings Of The 39th Course Of The International School Of Solid State Physics
Author: Antonio CricentiPublisher: World Scientific
ISBN: 9814471607
Category : Science
Languages : en
Pages : 191
Book Description
This special volume contains the proceedings of the 9th Epioptics Workshop, held at the Ettore Majorana Foundation and Centre for Scientific Culture, Erice, Sicily, from July 20 to 26, 2006. The workshop was the 9th in the Epioptics series and the 39th of the International School of Solid State Physics.The workshop was aimed at assessing the capabilities of state-of-the-art optical techniques in elucidating the fundamental electronic and structural properties of semiconductor and metal surfaces, interfaces, thin layers, and layer structures, and at assessing the usefulness of these techniques for optimization of high-quality multilayer samples through feedback control during materials growth and processing. Particular emphasis is dedicated to the theory of non-linear optics and to dynamical processes through the use of pump-probe techniques together with the search for new optical sources. Some new applications of scanning probe microscopy to material science and biological samples, dried and in vivo, with the use of different laser sources are also presented.
Advances in Nanoengineering
Author: A. Giles DaviesPublisher: Imperial College Press
ISBN: 1848160003
Category : Science
Languages : en
Pages : 328
Book Description
This book outlines a selection of exciting advances currently being made worldwide in the field of modern engineering at the nanometer scale. Leading scientists and engineers give a general overview of research advances in their specialized subject areas. They also describe some of their own cutting-edge research and give their visions of the future. Written in a popular and well-illustrated style, the articles are written by young scientists many of whom hold, or have held, prestigious Royal Society or EPSRC Fellowships. Carefully selected by Professor A G Davies and Professor J M T Thompson FRS, topics include: the fabrication and measurement of nanoelectronic devices, organic conductors, and bioelectronic materials; the assembly of such structures into appropriate configurations, including the use of biological processes to drive the assembly; the development of new materials including both organic and inorganic wires, carbon nanotubes, and magnetic materials; and finally, the analysis and characterization of these structures. The book conveys the excitement and enthusiasm of the authors for their work at the frontiers of modern engineering nanotechnology. All are definitive reviews for readers with a general interest in the future directions of science and engineering at the nanometer scale. Sample Chapter(s). Introduction (169 KB). Chapter 1: The Shape of Carbon: Novel Materials for the 21st Century (3,001 KB). Contents: The Shape of Carbon: Novel Materials for the 21st Century (H Terrones & M Terrones); Inorganic Nanowires (C Ducati); Multilayered Materials: A Palette for the Materials Artist (J M Molina-Aldareguia & S J Lloyd); Nature as Chief Engineer (S R Hall); Supramolecular Chemistry: The OC Bottom UpOCO Approach to Nanoscale Systems (P A Gale); Molecular Self-Assembly: A Toolkit for Engineering at the Nanometer Scale (C Wnlti); Exploring Tunnel Transport Through Protein at the Molecular Level (J J Davis et al.); Two Frontiers of Electronic Engineering: Size and Frequency (J Cunningham); Erasable Electrostatic Lithography to Fabricate Quantum Devices (R Crook); Ultrafast Nanomagnets: Seeing Data Storage in a New Light (R J Hicken); Near-Field Microscopy: Throwing Light on the Nanoworld (D Richards); Small Things Bright and Beautiful: Single Molecule Fluorescence Detection (M A Osborne). Readership: Graduate students, academics and researchers in nanotechnology. General audience with a scientific background at degree level."
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