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Spin Dependent Electron Behaviour In Quantum Point Contacts And Dots
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Book Synopsis Spin-Dependent Electron Behaviour in Quantum Point Contacts and Dots by : A. M. Bychkov
Download or read book Spin-Dependent Electron Behaviour in Quantum Point Contacts and Dots written by A. M. Bychkov and published by . This book was released on 2000 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt: We investigate theoretically the effect of spontaneous electron spin polarization in quantum point contacts and quantum dots. Self-consistent calculation process has been developed in the framework of Kohn-Sham LSDA scheme. The existence of the detected spin-polarized states in the low-density regime can be used to explain an anomalous 0.7-structure in the conductance of quantum point contacts. The properties of the potential device based on such an effect are briefly discussed.
Book Synopsis Electron Spin Transport in Quantum Dots and Point Contacts by : Erik Johan Koop
Download or read book Electron Spin Transport in Quantum Dots and Point Contacts written by Erik Johan Koop and published by . This book was released on 2008 with total page 132 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Spin-dependent Transport Phenomena in Single and Coupled Quantum Point Contacts by : Alexandros Shailos
Download or read book Spin-dependent Transport Phenomena in Single and Coupled Quantum Point Contacts written by Alexandros Shailos and published by . This book was released on 2004 with total page 222 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Quantum Dots written by Peter A. Ling and published by Nova Publishers. This book was released on 2005 with total page 170 pages. Available in PDF, EPUB and Kindle. Book excerpt: Since first developed in the early sixties, silicon chip technology has made vast leaps forward. From a rudimentary circuit with a mere handful of transistors, the chip has evolved into a technological wonder, packing millions of bits of information on a surface no larger that a human thumbnail. And most experts predict that in the near future, we will see chips with over a billion bits. Quantum dots are small devices that contain a tiny droplet of free electrons. They are fabricated in semiconductor materials and have typical dimensions ranging from nanometres to a few microns. The size and shape of these structures and therefore the number of electrons they contain can be precisely controlled; a quantum dot can have anything from a single electron to a collection of several thousands. The physics of quantum dots shows many parallels with the behaviour of naturally occurring quantum systems in atomic and nuclear physics. As in an atom, the energy levels in a quantum dot become quantised due to the confinement of electrons. Unlike atoms however, quantum dots can be easily connected to electrodes and are therefore excellent tools for studying atomic-like properties. This new book brings together leading research from throughout the world in this field of the future which has become the field of today.
Book Synopsis Electronic Interactions in Semiconductor Quantum Dots and Quantum Point Contacts by : Tai-Min Liu
Download or read book Electronic Interactions in Semiconductor Quantum Dots and Quantum Point Contacts written by Tai-Min Liu and published by . This book was released on 2011 with total page 109 pages. Available in PDF, EPUB and Kindle. Book excerpt: We report several detailed experiments on electron transport through Quantum Point Contacts (QPCs) and lateral Quantum Dots (QDs), created in a Single-Electron Transistor (SET). In the experiment for QPCs, we present a zero-bias peak (ZBP) in the differential conductance, G, which splits in an external magnetic field. The observed splitting closely matches the Zeeman energy and shows very little dependence on gate voltage, suggesting that the mechanism responsible for the formation of the peak involves electron spin. We also show that the mechanism that leads to the formation of the ZBP is different from the conventional Kondo effect found in QDs. In the second experiment, we present transport measurements of a QD in a spin-flip cotunneling regime and a quantitative comparison of the data to the microscopic theory by Lehman and Loss. The differential conductance is measured in the presence of an in-plane Zeeman field. We focus on the ratio of the nonlinear G at bias voltages exceeding the Zeeman threshold to G for those below the threshold. The data show good quantitative agreement with the theory with no adjustable parameters. We also compare the theoretical results to the predictions of a phenomenological form used for the determination of a heterostructure g-factor and find good agreement between the two. In the third experiment, we report the magnetic splitting, [Delta] K, of a Kondo peak in G for a QD while tuning the Kondo temperature, TK, along two different paths in the parameter space: varying the dot-lead coupling at a constant dot energy, and vice versa. At a high magnetic field, B, the changes of [Delta] K with TK along the two paths have opposite signs, indicating that [Delta] K is not a universal function of TK. At low B, we observe a decrease in [Delta]K with TK along both paths, in agreement with theoretical predictions. Furthermore, we find [Delta] K / [Delta]1 at low B and [Delta] K / [Delta] 1 at high B, where [Delta] is the Zeeman energy of the bare spin, in the same system. In the last experiment, we report the zero-bias differential conductance, of an SET in the Kondo regime as a function of temperature, T, and an in-plane magnetic field B. Scaled plots of both the T- and B-dependent data show universal behavior. At moderate and high B, the magnetoconductance data show good agreement with renormalization group calculations in the spin-1/2 Kondo regime. At very low B, we observe a non-monotonic behavior, which may due to the presence of multiple orbital dot levels with similar energies. Further study is required to confirm this assumption.
Book Synopsis Electron Transport in Quantum Dots by : Jonathan P. Bird
Download or read book Electron Transport in Quantum Dots written by Jonathan P. Bird and published by Springer Science & Business Media. This book was released on 2013-11-27 with total page 481 pages. Available in PDF, EPUB and Kindle. Book excerpt: When I was contacted by Kluwer Academic Publishers in the Fall of 200 I, inviting me to edit a volume of papers on the issue of electron transport in quantum dots, I was excited by what I saw as an ideal opportunity to provide an overview of a field of research that has made significant contributions in recent years, both to our understanding of fundamental physics, and to the development of novel nanoelectronic technologies. The need for such a volume seemed to be made more pressing by the fact that few comprehensive reviews of this topic have appeared in the literature, in spite of the vast activity in this area over the course of the last decade or so. With this motivation, I set out to try to compile a volume that would fairly reflect the wide range of opinions that has emerged in the study of electron transport in quantum dots. Indeed, there has been no effort on my part to ensure any consistency between the different chapters, since I would prefer that this volume instead serve as a useful forum for the debate of critical issues in this still developing field. In this matter, I have been assisted greatly by the excellent series of articles provided by the different authors, who are widely recognized as some of the leaders in this vital area of research.
Book Synopsis Electron Spin and Charge in Semiconductor Quantum Dots by : Jeroen Martijn Elzerman
Download or read book Electron Spin and Charge in Semiconductor Quantum Dots written by Jeroen Martijn Elzerman and published by Delft University Press. This book was released on 2004-01-01 with total page 147 pages. Available in PDF, EPUB and Kindle. Book excerpt: Introduction, Few-electron quantum dot circuit with integrated charge read-out, Excited-state spectroscopy on a nearly closed quantum dot via charge detection, Real-time detection of single electron tunneling using a quantum point contact, Single-shot read-out of an individual electron spin in a quantum dot, Semiconductor few-electron quantum dots as spin qubits, the Kondo effect in the unitary limit, Kondo effect in an integer-spin quantum dot, Electron cotunneling in a semiconductor dot, Summary.
Download or read book Quantum Dots written by Lucjan Jacak and published by Springer Science & Business Media. This book was released on 2013-06-29 with total page 176 pages. Available in PDF, EPUB and Kindle. Book excerpt: We present an overview of the theoretical background and experimental re sults in the rapidly developing field of semiconductor quantum dots - systems 8 6 of dimensions as small as 10- -10- m (quasi-zero-dimensional) that contain a small and controllable number (1-1000) of electrons. The electronic structure of quantum dots, including the energy quan tization of the single-particle states (due to spatial confinement) and the evolution of these (Fock-Darwin) states in an increasing external magnetic field, is described. The properties of many-electron systems confined in a dot are also studied. This includes the separation of the center-of-mass mo tion for the parabolic confining potential (and hence the insensitivity of the transitions under far infrared radiation to the Coulomb interactions and the number of particles - the generalized Kohn theorem) and the effects due to Coulomb interactions (formation of the incompressible magic states at high magnetic fields and their relation to composite jermions), and finally the spin-orbit interactions. In addition, the excitonic properties of quantum dots are discussed, including the energy levels and the spectral function of a single exciton, the relaxation of confined carriers, the metastable states and their effect on the photoluminescence spectrum, the interaction of an exciton with carriers, and exciton condensation. The theoretical part of this work, which is based largely on original re sults obtained by the authors, has been supplemented with descriptions of various methods of creating quantum-dot structures.
Book Synopsis Spin-dependent Electron Dynamics in a Lateral Triple Quantum Dot by : Maria Busl
Download or read book Spin-dependent Electron Dynamics in a Lateral Triple Quantum Dot written by Maria Busl and published by . This book was released on 2007 with total page 81 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis The Physics of Nanoelectronics by : Tero T. Heikkilä
Download or read book The Physics of Nanoelectronics written by Tero T. Heikkilä and published by Oxford University Press, USA. This book was released on 2013-01-31 with total page 296 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book provides an introduction to phenomena and models in nanoelectronics. It starts from the basics, but also introduces topics of recent interest, such as superconducting qubits, graphene, and quantum nanoelectromechanics.
Book Synopsis Quantum Engineering by : A. M. Zagoskin
Download or read book Quantum Engineering written by A. M. Zagoskin and published by Cambridge University Press. This book was released on 2011-07-14 with total page 345 pages. Available in PDF, EPUB and Kindle. Book excerpt: Quantum engineering – the design and fabrication of quantum coherent structures – has emerged as a field in physics with important potential applications. This book provides a self-contained presentation of the theoretical methods and experimental results in quantum engineering. The book covers topics such as the quantum theory of electric circuits, theoretical methods of quantum optics in application to solid state circuits, the quantum theory of noise, decoherence and measurements, Landauer formalism for quantum transport, the physics of weak superconductivity and the physics of two-dimensional electron gas in semiconductor heterostructures. The theory is complemented by up-to-date experimental data to help put it into context. Aimed at graduate students in physics, the book will enable readers to start their own research and apply the theoretical methods and results to their current experimental situation.
Book Synopsis Nonequilibrium Electron Transport in Quantum Dot and Quantum Point Contact Systems by : Anasuya Erin Krishnaswamy
Download or read book Nonequilibrium Electron Transport in Quantum Dot and Quantum Point Contact Systems written by Anasuya Erin Krishnaswamy and published by . This book was released on 1999 with total page 286 pages. Available in PDF, EPUB and Kindle. Book excerpt: Much experimental research has been performed in the equilibrium regime on individual quantum dots and quantum point contacts (QPCs). The focus of the research presented here is electron transport in the nonequilibrium regime in coupled quantum dot and QPC systems fabricated on AlGaAs/GaAs material using the split gate technique. Near equilibrium magnetoconductance measurements were performed on a quantum dot and a QPC. Oscillations were seen in the conductance of the sensor which corresponded to Aharonov-Bohm oscillations in the quantum dot, to our knowledge the first such observation. Sudden jumps in the conductance of the QPC were observed under certain gate biases and under certain magnetic fields. When the gate biases and magnetic field were held constant and the conductance was observed over time, switching was observed with the form of a random telegraph signal (RTS). RTS switching is usually attributed to charging of a single impurity. However, in this case switching may have been due to tunneling via edge states in the dot. Nonequilibrium transport in single quantum dots was investigated. A knee or kink was observed in the current-voltage characteristics of two dots on different material. The bias conditions under which the knee occurred point to electron heating as the physical mechanism for the observed behavior. However, the data can not be fit accurately over all bias ranges with an energy balance hot electron model. Modifications to the model are needed to accurately represent the devices studied here. Finally, the effect of nonlinear transport through a one dimensional (1D) QPC on the equilibrium conductance of an adjacent OD quantum dot was explored. This was the first attempt to observe Coulomb drag between a OD and 1D system. It was observed that the equilibrium conductance peaks in the quantum dot were broadened as the current in the QPC increased. This apparent electron heating effect in the dot can be explained by a simple ballistic phonon model. However, reasonable phase coherence times can be estimated from peak fitting using a Breit- Wigner formula which points to a Coulomb interaction. More detailed numerical calculations should illuminate the dominant scattering processes.
Book Synopsis Readout of Electron Spins in Quantum Point Contacts by : Youngsoo Yoon
Download or read book Readout of Electron Spins in Quantum Point Contacts written by Youngsoo Yoon and published by . This book was released on 2008 with total page 149 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis is motivated by recent interest in the binding of single spins on quantum point contacts (QPCs). While this regime is inaccessible to experiments performed on single QPCs, this thesis provides strong evidence for the spin binding by studying the interaction between coupled QPCs, one of which is biased in the regime where the spin binding is expected to occur. Thus, this thesis describes a series of experiments aimed at understanding and manipulating single electron spins confined in QPCs, with the long term goal of the implementation of a QPC-based quantum computer. In these experimental studies, we demonstrate a resonant interaction between closely coupled QPCs due to bound-state formation, and show that this may give rise to robust confinement of single spins, which show clear Zeeman splitting in a magnetic field. Our experimental investigations of the resonance exhibited by coupled QPCs clearly show that this feature is consistent with the Fano form, providing strong independent support for the idea of bound-state formation in QPCs near pinch-off. Although the Fano mechanism is typically the dominant effect responsible for the coupled-QPC interaction, we also demonstrate evidence of a crossover from Fano to Coulomb coupling between the QPCs as their wavefunction overlap, and so the Fano mechanism, is suppressed. We show also that the coupling strength characterizing the Fano effect grows as the two QPCs are brought closer to one another. Finally, we discuss the observation of a novel nonlinear Fano effect, by using source-drain bias spectroscopy of coupled QPCs. The key result here is that the coupling strength between the resonant and non-resonant paths can be tuned in situ, starting from weak coupling in the linear (small source-drain bias) regime but becoming stronger at large bias.
Book Synopsis Spin Effects in Quantum Point Contacts by : Yuan Ren
Download or read book Spin Effects in Quantum Point Contacts written by Yuan Ren and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Lateral Quantum Dots for Quantum Information Processing by : Matthew Gregory House
Download or read book Lateral Quantum Dots for Quantum Information Processing written by Matthew Gregory House and published by . This book was released on 2012 with total page 168 pages. Available in PDF, EPUB and Kindle. Book excerpt: The possibility of building a computer that takes advantage of the most subtle nature of quantum physics has been driving a lot of research in atomic and solid state physics for some time. It is still not clear what physical system or systems can be used for this purpose. One possibility that has been attracting significant attention from researchers is to use the spin state of an electron confined in a semiconductor quantum dot. The electron spin is magnetic in nature, so it naturally is well isolated from electrical fluctuations that can a loss of quantum coherence. It can also be manipulated electrically, by taking advantage of the exchange interaction. In this work we describe several experiments we have done to study the electron spin properties of lateral quantum dots. We have developed lateral quantum dot devices based on the silicon metal-oxide-semiconductor transistor, and studied the physics of electrons confined in these quantum dots. We measured the electron spin excited state lifetime, which was found to be as long as 30 ms at the lowest magnetic fields that we could measure. We fabricated and characterized a silicon double quantum dot. Using this double quantum dot design, we fabricated devices which combined a silicon double quantum dot with a superconducting microwave resonator. The microwave resonator was found to be sensitive to two-dimensional electrons in the transistor channel, which we measured and characterized. We developed a new method for extracting information from random telegraph signals, which are produced when we observe thermal fluctuations of electrons in quantum dots. The new statistical method, based on the hidden Markov model, allows us to detect spin-dependent effects in such fluctuations even though we are not able to directly observe the electron spin. We use this analysis technique on data from two experiments involving gallium arsenide quantum dots and use it to measure spin-dependent tunneling rates. Our results advance the understanding of electron spin physics in lateral quantum dots, in silicon and in gallium arsenide.
Book Synopsis Quantum Confined States and Room Temperature Spin Coherence in Semiconductor Nanocrystal Quantum Dots by : Ahmad Khastehdel Fumani
Download or read book Quantum Confined States and Room Temperature Spin Coherence in Semiconductor Nanocrystal Quantum Dots written by Ahmad Khastehdel Fumani and published by . This book was released on 2015 with total page 103 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this thesis we studied the signature of quantum confined electronic structure of CdSe nanocrystal quantum dots (NCQDs) in the electron spin behavior via time resolved Faraday rotation (TRFR) measurement at room temperature. We found that there is a distinction between the optical spin pumping efficiency(SPE) spectrum and the optical absorbance. Although the first peak in the SPE coincides with the band edge absorption peak, the rest of the two spectra show significant distinctions. There is a second peak in the signal from the larger NCQDs 200~meV higher in energy. The SPE diminishes afterwards. In smaller NCQDs there is only one peak in the signal. We model this behavior following a 6-band effective mass approximation spin dependent absorbance calculation. We also investigated the dynamics of the spin signal and the presence of two precessing components in the TRFR signal. We find that the inhomogeneous dephasing is not sufficient to explain the dynamics of both components. We associate one of the components to the spin signal from neutral excitons and the other one to positively charged trions. We describe the data using a magnetic field dependent spin decoherence mechanism that occurs via fluctuation of the exciton energy levels in between the available fine structure states. This model captures the TRFR experiment data on both short and long timescales. Additionally, we developed a NCQD-polymer composite optical waveguide and investigated the optical spin measurement on these structures.
Book Synopsis Concepts in Spin Electronics by : Sadamichi Maekawa
Download or read book Concepts in Spin Electronics written by Sadamichi Maekawa and published by OUP Oxford. This book was released on 2006-01-26 with total page 416 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nowadays information technology is based on semiconductor and ferromagnetic materials. Information processing and computation are based on electron charge in semiconductor transistors and integrated circuits, and information is stored on magnetic high-density hard disks based on the physics of the electron spins. Recently, a new branch of physics and nanotechnology, called magneto-electronics, spintronics, or spin electronics, has emerged, which aims at simultaneously exploiting both the charge and the spin of electrons in the same device. A broader goal is to develop new functionality that does not exist separately in a ferromagnet or a semiconductor. The aim of this book is to present new directions in the development of spin electronics in both the basic physics and the technology which will become the foundation of future electronics.
