Download or read book Spin Coherence and Vibrational Tunneling in Coupled Quantum Dot Pairs written by Cameron Lamar Jennings and published by . This book was released on 2020 with total page 204 pages. Available in PDF, EPUB and Kindle. Book excerpt: Quantum dots (QDs) are semiconductor nanoparticles that trap electrons and holes in all three dimensions, resulting in discrete energy levels with strong optical transitions. InAs/GaAs QDs are grown by molecular beam epitaxy of lattice-mismatched InAs on a GaAs substrate, resulting in strain-induced island formation on a two-dimensional wetting layer. In addition to optoelectronic applications such as lasing, infrared detection, and photovoltaics, QDs are capable of hosting optically-controlled spin qubits and emitting photonic qubits for quantum communication and quantum computation. This dissertation focuses on InAs/GaAs coupled quantum dot pairs (CQDs) formed by strain-induced alignment of QDs in nearby layers, resulting in interdot charge tunneling that can be controlled with an applied electric field. We use a combination of theoretical modeling and optical spectroscopy to understand dynamical processes of bound photoexcited charges, aiming to enhance their usefulness for quantum information and sensing technologies and help overcome difficulties preventing their implementation. We develop a model of electron and hole confinement in CQDs, including Coulomb and spin interactions, phonon coupling, and optical transitions. This model is used to simulate relaxation dynamics during neutral molecular biexciton cascades, identifying parameter regimes where two-photon polarization entanglement can be expected. While this process has been demonstrated in single QDs, we find that charge separation in interdot states of CQDs allows for tunable emission energies and a higher tolerance to anisotropic electron-hole exchange splitting. Using low-temperature optical photoluminescence spectrosopy, we identify charge and spin states in single CQDs and investigate their interactions. Two-laser photoluminescence excitation spectroscopy demonstrates two-photon excitation into the molecular biexciton state via a stepwise process, while calculations identify conditions required for efficient simultaneous two-photon absorption. Further investigations find decoherence by electric field fluctuations from charged lattice defects, and identify a novel enhancement of acoustic phonon coupling at hole tunneling resonances from piezoelectric interactions.
Download or read book Functionalization of Resonant Interactions in Coupled Quantum Dots written by and published by . This book was released on 2017 with total page 304 pages. Available in PDF, EPUB and Kindle. Book excerpt: The focus of this dissertation is discovering and finding functional uses of resonant interactions that occur in coupled quantum dots (i.e. quantum dot molecules, QDMs). Coupled quantum dots compared to individual quantum dots offer a more versatile platform to study interactions between photons, charges, and phonons. Applying an electric field in a QDM system allows tuning of the electronic energy states and controls particle tunneling between quantum dots, thus coupling the quantum dots. For the past two decades, extensive research into coupled quantum dot systems has led to a deeper understanding and control of the charge, spin and photonic properties of single quantum states. This dissertation continues the pursuit to further understand these QDM systems with a particular emphasis on exploring the physics of resonant interactions between electronic states, phononic states, and optical transitions. This work consists of three components, the first is a novel experimental method that is capable of achieving high resolution spectra. The second addresses the resonant interaction between discrete neutral exciton and optical phonons that generates a molecular polaron, which can be tuned to render QDM emissions transparent or amplify weak transitions. The final component addresses ultrafast optical charging into specific charge states of a QDM. In the first research chapter we report on an optical spectroscopy method which is capable of resolving spectral features beyond that of the spin fine structure and homogeneous linewidth of single quantum dots using a standard, easy to use spectrometer setup. This method incorporates both laser and photoluminescence spectroscopy, combining the advantage of laser linewidth limited resolution with multi-channel photoluminescence detection. Using this method allows the ability of greatly improving the resolution beyond that of a common single stage spectrometer. The method uses phonons to assist in the measurement of the photoluminescence of a single quantum dot after resonant excitation of its ground state transition. The phonons allow us to separate and filter out the elastically scattered excitation laser light. An advantageous feature of this method is that it is easily incorporated into standard spectroscopy set-ups, being accessible to a number of researchers. In the second research chapter we report on the coherent interaction between photons and phonons mediated by quantum dot molecular excitons. Fano resonances occur between an indirect discrete state and the optical phonon band's continuum of states. This quantum interference is highly tunable with excitation energy and laser power and allows for the phonons to behave in a coherent and non-dissipative manner. This feature has led to rendering QDM optical transitions transparent and can alternately be used to amplify weak coupling channels. This finding, using phonons in a coherent manner, can lead to new technologies in the emerging field of phononics. In the third research chapter we report on optical charging of quantum dot molecules. The excited state spectra of the neutral and singly charged excitons in QDMs are being studied via photoluminescence excitation spectroscopy (PLE). We find an anti-correlated behavior of the resonances in the PLE spectra of different charge states, allowing for selective optical charging of the QDMs. The PLE spectra are analyzed across the regions of resonances between the indirect exciton and excited direct transitions of the low energy dot of the dot pair. The charging process seen in the excited state spectra of the trion and neutral exciton is explained by the competition between various transition rates at the resonance between the two charge states. These distinct resonances are examples of optical charging and de-charging process within the QDM. We present the experimental results and mathematical model describing this charging process.
Download or read book Spin and Tunneling Effects in Coupled Quantum Dots written by Swati Ramanathan and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The One Dimensional Hubbard Model written by Fabian H. L. Essler and published by Cambridge University Press. This book was released on 2005-02-07 with total page 692 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents an account of the exact solution of the Hubbard model in one dimension. The early chapters develop a self-contained introduction to Bethe's ansatz and its application to the one-dimensional Hubbard model. The later chapters address more advanced topics.
Download or read book On the Interactions Between Charges Phonons and Photons in Electric Field Tunable Quantum Dot Molecules written by and published by . This book was released on 2001 with total page 420 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation focuses on the optical properties of single InAs/GaAs quantum dot molecules. A quantum dot molecule consists of a pair of quantum dots coupled by a nanometer scale tunneling barrier. Compared to single quantum dots, quantum dot molecules provide greatly enhanced versatility - with the ease of an electric field control, one gains broad flexibility to tune electronic energy levels and manipulate particle tunneling within a QDM. As a consequence, individual QDMs are being intensely studied as controllable interfaces of charge, spin and photonic quantum states at the single particle level. On the other hand, phonons - the quantized vibrations of the underlying crystal lattice - have mostly been left outside the realm of coherent control. In the domain of solid-state quantum technologies, the ubiquitous phonons are mainly considered for the limitations they impose. Omnipresent electron-phonon interactions and the predominantly dissipative nature of phonons are typically a major source of decoherence of the atom-like quantum states hosted by low-dimensional solid-state structures, such as QDMs. Here, we report experimental and theoretical results on the interactions between charges, photons and phonons in electric field tunable quantum dot molecules. Using an effective mass perturbation model, we compute the low energy biexciton states of a quantum dot molecule and apply them to provide a theoretical description of the dipole-dipole interaction between two excitons occupying separate dots in a quantum dot molecule. The expected properties of these so called dipolar states are presented, and we highlight their potential application as a switch for manipulating the transition energy and tunneling properties of the ground state neutral exciton. We then present results from a comprehensive investigation of the quantum confined Stark effect in quantum dot molecules, in which we studied the electric-field dependent energy shifts of exciton states as a function of the tunneling barrier width. Our experimental and computational results reveal that molecular wavefunction formation in quantum dot molecules strongly affects the quantum confined Stark effect, even as the dots are tuned far from resonance for particle tunneling. This dissertation culminates with our report of a novel mechanism by which phonons are made non-dissipative and coherent via electric field control and the optically driven formation of a molecular polaron in a quantum dot molecule. The coherent interaction of a single optical phonon with individual electronic states is revealed via a Fano-type quantum interference that produces a phonon-induced transparency in the optical absorption of individual quantum dot molecules. Experimentally, we find that the transparency is widely tunable by electronic and optical means, and provides a mechanism for amplifying weak coupling channels. This work is significant in that it demonstrates a specific mechanism by which typically incoherent and dissipative phonons are made to behave in a coherent and non-dissipative manner. As such, we demonstrate that phonons may enter the realm of mutual control of quantum states on the single particle level, which so far has been dominated by photons, electrons and spins.
Download or read book Molecular Magnets written by Juan Bartolomé and published by Springer Science & Business Media. This book was released on 2013-10-17 with total page 401 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book provides an overview of the physical phenomena discovered in magnetic molecular materials over the last 20 years. It is written by leading scientists having made the most important contributions to this active area of research. The main topics of this book are the principles of quantum tunneling and quantum coherence of single-molecule magnets (SMMs), phenomena which go beyond the physics of individual molecules, such as the collective behavior of arrays of SMMs, the physics of one-dimensional single–chain magnets and magnetism of SMMs grafted on substrates. The potential applications of these physical phenomena to classical and quantum information, communication technologies, and the emerging fields of molecular spintronics and magnetic refrigeration are stressed. The book is written for graduate students, researchers and non-experts in this field of research.
Download or read book Electron Spin Echo Envelope Modulation ESEEM Spectroscopy written by Sergei A. Dikanov and published by CRC Press. This book was released on 1992-07-27 with total page 432 pages. Available in PDF, EPUB and Kindle. Book excerpt: The first volume devoted entirely to Electron Spin Echo Envelope Modulation (ESEEM) Spectroscopy This valuable book provides an introduction and broad survey of topics in ESEEM spectroscopy, including the theory, instrumentation, peculiarities of ESE experiments, and analysis of experimental data with particular emphasis on orientationally disordered systems. Applications of ESEEM spectroscopy to study chemically and biologically important paramagnetic centers in single crystals, amorphous solids, and powders are discussed as well. Electron Spin Echo Envelope Modulation (ESEEM) Spectroscopy will benefit specialists in magnetic resonance spectroscopy, physicists, chemists, and biologists who use magnetic resonance in their research.
Download or read book Handbook of Spintronics written by Yongbing Xu and published by Springer. This book was released on 2015-10-14 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Over two volumes and 1500 pages, the Handbook of Spintronics will cover all aspects of spintronics science and technology, including fundamental physics, materials properties and processing, established and emerging device technology and applications. Comprising 60 chapters from a large international team of leading researchers across academia and industry, the Handbook provides readers with an up-to-date and comprehensive review of this dynamic field of research. The opening chapters focus on the fundamental physical principles of spintronics in metals and semiconductors, including an introduction to spin quantum computing. Materials systems are then considered, with sections on metallic thin films and multilayers, magnetic tunnelling structures, hybrids, magnetic semiconductors and molecular spintronic materials. A separate section reviews the various characterisation methods appropriate to spintronics materials, including STM, spin-polarised photoemission, x-ray diffraction techniques and spin-polarised SEM. The third part of the Handbook contains chapters on the state of the art in device technology and applications, including spin valves, GMR and MTJ devices, MRAM technology, spin transistors and spin logic devices, spin torque devices, spin pumping and spin dynamics and other topics such as spin caloritronics. Each chapter considers the challenges faced by researchers in that area and contains some indications of the direction that future work in the field is likely to take. This reference work will be an essential and long-standing resource for the spintronics community.
Download or read book Transport in Weakly Coupled Vertical Double Quantum Dots written by Christopher Payette and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Theory of Spin Relaxation in Laterally Coupled Quantum Dots written by Martin Raith and published by Universitatsverlag Regensburg. This book was released on 2013-09-10 with total page 120 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Lifetime and Coherence of the Coupled Electron and Nuclear Spin Systems in Semiconductor Quantum Dots written by George Gillard and published by . This book was released on 2022 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Coherence and Correlation Effects in Coupled Quantum Dot Systems written by Stefan Legel and published by . This book was released on 2008 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Graphene Quantum Dots written by Alev Devrim Güçlü and published by Springer. This book was released on 2014-09-11 with total page 181 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book reflects the current status of theoretical and experimental research of graphene based nanostructures, in particular quantum dots, at a level accessible to young researchers, graduate students, experimentalists and theorists. It presents the current state of research of graphene quantum dots, a single or few monolayer thick islands of graphene. It introduces the reader to the electronic and optical properties of graphite, intercalated graphite and graphene, including Dirac fermions, Berry's phase associated with sublattices and valley degeneracy, covers single particle properties of graphene quantum dots, electron-electron interaction, magnetic properties and optical properties of gated graphene nanostructures. The electronic, optical and magnetic properties of the graphene quantum dots as a function of size, shape, type of edge and carrier density are considered. Special attention is paid to the understanding of edges and the emergence of edge states for zigzag edges. Atomistic tight binding and effective mass approaches to single particle calculations are performed. Furthermore, the theoretical and numerical treatment of electron-electron interactions at the mean-field, HF, DFT and configuration-interaction level is described in detail.
Download or read book Advances in Chemical Physics written by Ilya Prigogine and published by John Wiley & Sons. This book was released on 2003-04-23 with total page 608 pages. Available in PDF, EPUB and Kindle. Book excerpt: Advances in Chemical Physics covers recent advances at the cutting edge of research relative to chemical physics. The series, Advances in Chemical Physics, provides a forum for critical, authoritative evaluations of advances in every area of the discipline.
Download or read book Quantum Computing written by National Academies of Sciences, Engineering, and Medicine and published by National Academies Press. This book was released on 2019-04-27 with total page 273 pages. Available in PDF, EPUB and Kindle. Book excerpt: Quantum mechanics, the subfield of physics that describes the behavior of very small (quantum) particles, provides the basis for a new paradigm of computing. First proposed in the 1980s as a way to improve computational modeling of quantum systems, the field of quantum computing has recently garnered significant attention due to progress in building small-scale devices. However, significant technical advances will be required before a large-scale, practical quantum computer can be achieved. Quantum Computing: Progress and Prospects provides an introduction to the field, including the unique characteristics and constraints of the technology, and assesses the feasibility and implications of creating a functional quantum computer capable of addressing real-world problems. This report considers hardware and software requirements, quantum algorithms, drivers of advances in quantum computing and quantum devices, benchmarks associated with relevant use cases, the time and resources required, and how to assess the probability of success.
Download or read book Physics Briefs written by and published by . This book was released on 1994 with total page 934 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Spin orbit Coupling Effects in Two Dimensional Electron and Hole Systems written by Roland Winkler and published by Springer Science & Business Media. This book was released on 2003-10-10 with total page 244 pages. Available in PDF, EPUB and Kindle. Book excerpt: The first part provides a general introduction to the electronic structure of quasi-two-dimensional systems with a particular focus on group-theoretical methods. The main part of the monograph is devoted to spin-orbit coupling phenomena at zero and nonzero magnetic fields. Throughout the book, the main focus is on a thorough discussion of the physical ideas and a detailed interpretation of the results. Accurate numerical calculations are complemented by simple and transparent analytical models that capture the important physics.
