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Indirect Excitons In Gaas Coupled Quantum Wells
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Book Synopsis Exciton Transport Phenomena in GaAs Coupled Quantum Wells by : Jason Leonard
Download or read book Exciton Transport Phenomena in GaAs Coupled Quantum Wells written by Jason Leonard and published by Springer. This book was released on 2017-11-02 with total page 67 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis presents results crucial to the emerging field of indirect excitons. These specially designed quasiparticles give the unique opportunity to study fundamental properties of quantum degenerate Bose gases in semiconductors. Furthermore, indirect excitons allow for the creation of novel optoelectronic devices where excitons are used in place of electrons. Excitonic devices are explored for the development of advanced signal processing seamlessly coupled with optical communication. The thesis presents and describes the author's imaging experiments that led to the discovery of spin transport of excitons. The many firsts presented herein include the first studies of an excitonic conveyer, leading to the discovery of the dynamical localization-delocalization transition for excitons, and the first excitonic ramp and excitonic diode with no energy-dissipating voltage gradient.
Book Synopsis Indirect Excitons in GaAs Coupled Quantum Wells by : Alexander Arthur High
Download or read book Indirect Excitons in GaAs Coupled Quantum Wells written by Alexander Arthur High and published by . This book was released on 2012 with total page 124 pages. Available in PDF, EPUB and Kindle. Book excerpt: Indirect excitons in coupled quantum wells form a unique system for both development of novel optoelectronic devices as well as studies of the low temperature physics of bosons in condensed matter systems. An exciton is a quasiparticle which is a bound state of an electron and hole. Excitons can be created by light, and when they recombine they can emit light. In an indirect exciton, the electron and hole are spatially separated, which results in a long exciton lifetime as well as an electronic dipole moment. The long lifetime allows excitons to travel over large distances ~ 100[mu]m. The electronic dipole moment allows direct electronic control of the exciton energy. Therefore, as an optical media that is also electronically controllable, indirect excitons offer promise for development of new, efficient optoelectronic devices. In this dissertation, we prototype two new optoelectronic devices based on indirect excitons : the exciton optoelectronic transistor, and the excitonic integrated circuit. In addition, the long radiative lifetime allows indirect excitons to cool to very low temperatures below the temperature of quantum degeneracy. Traps are of particular interest for studies of low temperature gases, as they facilitate creation of high density, cold gases as well as offer opportunities for in situ control of the gas. This dissertation presents novel, precisely engineered trapping potentials for exciton gases based on electronic control and makes a thorough examination of the physical properties of the trapped gas. Furthermore, as a bosonic quasiparticle, excitons can be expected to form a condensate under certain density and temperature conditions. A signature of condensation is the emergence of spontaneous extended coherence, where the coherence length significantly exceeds its classically expected value. We present the first evidence for extended spatial coherence in an exciton system - the system of exciton rings. A pattern of extended spontaneous coherence is correlated with a pattern of spontaneous polarization, revealing the properties of a multicomponent coherent state. We also observed phase singularities in the coherent exciton gas. Lastly, we probe the spatial coherence of excitons in an electrostatic trap and present direct evidence for Bose-Einstein condensation of excitons therein.
Book Synopsis Transport of Indirect Excitons in Coupled Quantum Wells by : Yuliya Yevgenyevna Kuznetsova
Download or read book Transport of Indirect Excitons in Coupled Quantum Wells written by Yuliya Yevgenyevna Kuznetsova and published by . This book was released on 2014 with total page 67 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation explores studies of transport of indirect excitons (bosonic quasiparticles composed of bound pairs of an electron and a hole confined to spatially separated layers) in GaAs coupled quantum wells. The small mass and long lifetime of indirect excitons result in a relatively high quantum degeneracy temperature and efficient cooling, making indirect excitons a model system for studies of physics of cold bosons. In addition, indirect excitons are optically active, electronically controllable and have long enough lifetimes that their transport distances can be accommodated by lithography. These properties make indirect excitons a promising system for creating excitonic devices. The direction of the research presented in this dissertation is thus twofold: studying fundamental physics of excitons, including transport, thermalization, coherence, spin currents, and properties in high magnetic fields, and realization of optical excitonic devices, such as traps and transistors.
Book Synopsis Spatially Indirect Excitons in Coupled Quantum Wells by : Chih-Wei Eddy Lai
Download or read book Spatially Indirect Excitons in Coupled Quantum Wells written by Chih-Wei Eddy Lai and published by . This book was released on 2004 with total page 362 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Exciton Transport Phenomena in GaAs Coupled Quantum Wells by : Jason R. Leonard
Download or read book Exciton Transport Phenomena in GaAs Coupled Quantum Wells written by Jason R. Leonard and published by . This book was released on 2016 with total page 83 pages. Available in PDF, EPUB and Kindle. Book excerpt: In GaAs excitons are optically active making them ideally suitable for optical communications and computation. An exciton is composite particle composed of an electron and hole. Indirect excitons are excitons with the electron and hole spatially separated into different quantum wells. Indirect excitons are oriented in the same direction allowing indirect excitons to be manipulated by voltage gradients. This dissertation explores controlling exciton transport with ramps--shaped electrodes that operate as excitonic diodes, or in a crossed ramp configuration operate as an optically controlled transistor. This dissertation also demonstrates an exciton conveyer--a moving lattice created by electrodes driven with AC voltages--that transports excitons over large distances. This dissertation concludes with an observation of exciton spin transport.
Book Synopsis Spatially Indirect Excitons in Coupled Quantum Wells by :
Download or read book Spatially Indirect Excitons in Coupled Quantum Wells written by and published by . This book was released on 2004 with total page 176 pages. Available in PDF, EPUB and Kindle. Book excerpt: Microscopic quantum phenomena such as interference or phase coherence between different quantum states are rarely manifest in macroscopic systems due to a lack of significant correlation between different states. An exciton system is one candidate for observation of possible quantum collective effects. In the dilute limit, excitons in semiconductors behave as bosons and are expected to undergo Bose-Einstein condensation (BEC) at a temperature several orders of magnitude higher than for atomic BEC because of their light mass. Furthermore, well-developed modern semiconductor technologies offer flexible manipulations of an exciton system. Realization of BEC in solid-state systems can thus provide new opportunities for macroscopic quantum coherence research. In semiconductor coupled quantum wells (CQW) under across-well static electric field, excitons exist as separately confined electron-hole pairs. These spatially indirect excitons exhibit a radiative recombination time much longer than their thermal relaxation time a unique feature in direct band gap semiconductor based structures. Their mutual repulsive dipole interaction further stabilizes the exciton system at low temperature and screens in-plane disorder more effectively. All these features make indirect excitons in CQW a promising system to search for quantum collective effects. Properties of indirect excitons in CQW have been analyzed and investigated extensively. The experimental results based on time-integrated or time-resolved spatially-resolved photoluminescence (PL) spectroscopy and imaging are reported in two categories. (i) Generic indirect exciton systems: general properties of indirect excitons such as the dependence of exciton energy and lifetime on electric fields and densities were examined. (ii) Quasi-two-dimensional confined exciton systems: highly statistically degenerate exciton systems containing more than tens of thousands of excitons within areas as small as (10 micrometer)2 were observed. The spatial and energy distributions of optically active excitons were used as thermodynamic quantities to construct a phase diagram of the exciton system, demonstrating the existence of distinct phases. Optical and electrical properties of the CQW sample were examined thoroughly to provide deeper understanding of the formation mechanisms of these cold exciton systems. These insights offer new strategies for producing cold exciton systems, which may lead to opportunities for the realization of BEC in solid-state systems.
Book Synopsis Hydrodynamics of Indirect Excitons in Coupled Quantum Wells by : Joe Wilkes
Download or read book Hydrodynamics of Indirect Excitons in Coupled Quantum Wells written by Joe Wilkes and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis comprises a theoretical study of the dynamics of indirect excitons in coupled quantum wells at low lattice temperatures. The results of numerical simulations of the exciton photoluminescence pattern are presented and compared to available experimental data. The in-plane transport of quantum well excitons created by laser excitation is modeled using a non-linear drift-diffusion equation. Combined with a model of exciton relaxation thermodynamics, a complete description of the evolution of the exciton density and temperature is built. The optical decay of indirect excitons is included in the modeling. This is used to make predictions of the spatial photoluminescence patterns which have been observed experimentally. The transport of dipole orientated excitons via externally applied electrostatic potentials is also studied. The drift-diffusion equation is adapted to include the inplane electric field. This is done for some specific forms of the potential landscapes such as a linear potential energy gradient and a propagating lattice. These correspond to some recent experiments for which results are available. The combined theoretical and experimental studies reveal a deeper insight into the transport properties of indirect excitons. Finally, the external ring structure in the indirect exciton emission pattern is studied. Its formation is modeled using a set of coupled transport equations for electrons, holes and indirect excitons. The Coulomb interactions between all three species are incorporated in the model. It is shown that these interactions lead to an instability in the external ring and are responsible for its fragmentation into a periodic array of islands which has been observed experimentally.
Book Synopsis Transport and Coherence Properties of Indirect Excitons in Coupled Quantum Wells by : Leonidas Mouchliadis
Download or read book Transport and Coherence Properties of Indirect Excitons in Coupled Quantum Wells written by Leonidas Mouchliadis and published by . This book was released on 2008 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Quantum Systems of Indirect Excitons in GaAs Heterostructures by : Darius Jamsheed Choksy
Download or read book Quantum Systems of Indirect Excitons in GaAs Heterostructures written by Darius Jamsheed Choksy and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Semiconductors have proven themselves to be an excellent platform for both the development of new technologies and the study of fundamental physics. Various semiconductor materials provide us the ability to control and study the bulk system behavior, electronic behavior, and light matter interactions. Of particular interest to this paper is the study of a quasi-particle that can form in semiconductors known as an exciton. Made from an electron and hole, it also has very useful photonic properties. In our work we study excitons created by photoexcitation, where a laser excites an electron from the lattice, creating an electron and hole, the electrons and holes created can then form a bound state known as an exciton. Excitons can transform into photons via radiative recombination. Our experiments typically deal with a system of quantum wells, engineered to keep the electrons and holes spatially separated, a bound pair of an electron and hole with the electron and hole in different quantum wells is known as an indirect exciton. Some of the properties of indirect excitons are an electric dipole moment, energy controlled by voltage, long lifetimes, macroscopic transport, and they are bosons. These properties as well as their interaction with light allow for systems to be created that act as proof-of-concept prototypes for excitonic devices, as well as a platform to study fundamental physics of cold bosons. The work in this dissertation is primarily focused on dipole-dipole attraction and the formation of a Fermi edge singularity in these systems. These works give us new insights into the interactions of bosons and formation of new states of matter.
Book Synopsis Studies of Transport and Thermalization of Excitons and the Development of Techniques for In-situ Manipulation of Excitons in Coupled Quantum Wells by : Aaron Tynes Hammack
Download or read book Studies of Transport and Thermalization of Excitons and the Development of Techniques for In-situ Manipulation of Excitons in Coupled Quantum Wells written by Aaron Tynes Hammack and published by . This book was released on 2010 with total page 168 pages. Available in PDF, EPUB and Kindle. Book excerpt: The study of excitons in semiconductors is a rich field that has seen numerous beautiful developments during the seven decades since they were proposed by Frenkel [1931]. The exciton states in dielectric materials and molecular complexes are fundamental to understanding the full electronic structure of materials and the complex interactions between light and matter. Of particular interest is the fact that excitons, bound electron-hole pairs, form composite bosons with very low effective masses. This opens up an incredibly rich opportunity to study the phase space of quantum degenerate Bose gases at relatively high temperatures. An overview of many of the rich features that have been observed in exciton gases is presented. The system of indirect excitons in coupled quantum wells (CQWs) provides for drastically increased and tunable exciton lifetimes, leading to improved thermalization. The present experimental study presents a full steady state and dynamic model for the transport, generation, recombination, and thermalization of indirect excitons in CQWs, as well as methods for in-situ manipulation of indirect excitons by both optical and electrical methods. Both the optical and electrical methods for exciton control provide for dynamic manipulation of excitons on timescales significantly shorter than the lifetimes of indirect excitons.
Book Synopsis Spontaneous Coherence, Kinetics and Pattern Formation in Cold Exciton Gases in GaAs/AlGaAs Coupled Quantum Wells by : Sen Yang
Download or read book Spontaneous Coherence, Kinetics and Pattern Formation in Cold Exciton Gases in GaAs/AlGaAs Coupled Quantum Wells written by Sen Yang and published by . This book was released on 2009 with total page 84 pages. Available in PDF, EPUB and Kindle. Book excerpt: Indirect excitons in GaAS/AlGaAs coupled quantum wells have small mass, long lifetime and short cooling time. Those enable us to create a cold exciton gas. I will present the experimental study of this cold exciton gas including kinetics, pattern formation and coherence. A spatial photoluminescence pattern including external exciton rings, localized bright spots, and the macroscopically ordered exciton state (MOES) was observed. While the external ring is a classical object by itself it is the region where the coldest exciton gas is created: the external ring is far from the hot excitation spot and the excitons in the ring are formed from well-thermalized carriers. The MOES - an array of beads with spatial order on macroscopic length appears abruptly in the ring at temperatures below a few Kelvin, where the thermal de Broglie wavelength is comparable to the interparticle separation and the exciton gas is nonclassical. We performed the first time-resolved kinetics measurements in this system. Simulations based on in-plane charge separation model gave good agreements with experimental results. From the simulation fits, diffusion constant of electrons and holes were obtained. We also observed commensurability in MOES: the exciton density wave is stable when there is an integer number of MOES wavelength between defects. In the external ring, a strong enhancement of spatial coherence length is observed below a few Kelvin. The increase of the coherence length is correlated with the macroscopic spatial ordering of excitons. The coherence length at the lowest temperature corresponds to a very narrow spread of the exciton momentum distribution, much smaller than that for a classical exciton gas.
Book Synopsis Subnanosecond Control of Excitons in Coupled Quantum Well Nanostructures by : Alexander Graham Winbow
Download or read book Subnanosecond Control of Excitons in Coupled Quantum Well Nanostructures written by Alexander Graham Winbow and published by . This book was released on 2010 with total page 280 pages. Available in PDF, EPUB and Kindle. Book excerpt: Indirect excitons in GaAs coupled quantum well nanostructures are a versatile system for fundamental study of cold neutral bosonic gases and demonstration of novel optoelectronic devices based on excitons -- a bound electron-hole pair -- rather than electrons. Indirect exciton lifetimes range from nanoseconds to microseconds and cool rapidly after photoexcitation to the lattice temperature. Lithographically-patterned electrodes enable design of potential energy landscapes, and both energy and lifetime can be controlled in situ, rapidly, on timescales much shorter than the exciton lifetime. Such intrinsically optoelectronic devices can operate at speeds relevant to optical networks, and later be fabricated in other semiconductors for higher-temperature operation. Two different kinds of devices are demonstrated Photon storage -- an optical memory -- with 250 ps rise time of the readout optical signal and storage time reaching microseconds was implemented with indirect excitons in CQW. The storage and release of photons was controlled by the gate voltage pulse, and the transient processes in the CQW studied by measuring the kinetics of the exciton emission spectra. This control of excitons on timescales much shorter than the exciton lifetime demonstrates the feasibility of studying excitons in in situ controlled electrostatic traps. The Exciton Conveyer is a laterally moving electrostatic lattice potential for actively transporting excitons. Generated by laterally modulated electrodes, the potential velocity and depth are controlled in situ by frequency and voltage. We observed exciton transport characterized by average exciton cloud spatial extension over several tens of microns, and observed dynamical localization-delocalization transitions for the excitons in the conveyer : In the localization regime of deeper potentials and moderate exciton density, excitons are moved by the conveyer; in the delocalized regime of shallower lattice potential or high exciton density, excitons do not follow the conveyer motion. We explore conveyer velocities both slower and faster than phonon velocities. Realizing subnanosecond manipulations of exciton energy and lifetime required versatile control of pulsed and multiple AC RF electrical signals in optical, liquid helium cryogenic systems. Considerable detail is presented of design, construction, and test of flexible experimental apparatus.
Book Synopsis Transport of Indirect Excitons in GaAs Heterostructures by : Matthew W. Hasling
Download or read book Transport of Indirect Excitons in GaAs Heterostructures written by Matthew W. Hasling and published by . This book was released on 2018 with total page 62 pages. Available in PDF, EPUB and Kindle. Book excerpt: Indirect excitons are bosonic quasiparticles composed of an electron and a hole confined to spatially separated quantum wells. Many properties of excitons, such as their low effective mass, long lifetime, tunable energy, and optically active nature, make them an ideal system for studying condensed matter phenomena. This dissertation explores the transport properties associated with indirect excitons in various environments. In this dissertation, exciton transport is studied in multiple devices, created by carefully patterned electrodes, which create a varied potential energy landscape for the excitons. The first device is used to trap large amounts of excitons, which can be used to study the properties of dense exciton gases. The second device is used as a stirring potential for indirect excitons, and can give excitons angular momentum while they collect to the center of the device. In addition, a record high quality single quantum well structure is characterized, which may prove to be a new platform for studying indirect excitons. Measurements of this new sample show large transport and a record high diffusion coefficient for indirect excitons.
Book Synopsis Thermalization, Diffusion and Photoluminescence of Statistically-degenerate Indirect Excitons in Coupled Quantum Wells by : Lois Elenid Smallwood
Download or read book Thermalization, Diffusion and Photoluminescence of Statistically-degenerate Indirect Excitons in Coupled Quantum Wells written by Lois Elenid Smallwood and published by . This book was released on 2006 with total page 120 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Proceedings of 2000 International Conference on Excitonic Processes in Condensed Matter by : Kikuo Cho
Download or read book Proceedings of 2000 International Conference on Excitonic Processes in Condensed Matter written by Kikuo Cho and published by World Scientific. This book was released on 2001 with total page 506 pages. Available in PDF, EPUB and Kindle. Book excerpt: At Yamada Conference LIII, papers on many novel materials and on novel phenomena in condensed matter physics were presented OCo for instance, the achievement of simultaneous creation of excitons and free-electron-hole pairs in rare gas solids, and a low frequency fluctuation of the spectral shift of indirect excitons in GaAs coupled quantum wells. Single molecule spectroscopy is a powerful tool for studying molecules including biological systems; the study of delocalization of excitons in the photosynthetic light harvesting antenna system was also reported. The proceedings thus contain many excellent papers dealing with current research topics on the excitonic processes in bulk, quantum wells, quantum dots and other confined systems. This book will serve as an excellent source of recent references and reviews for a wide range of researchers in physics, chemistry, engineering and biological sciences. The proceedings have been selected for coverage in: . OCo Index to Scientific & Technical Proceedings (ISTP CDROM version / ISI Proceedings). Contents: Dynamical Process of Photoionization in Semiconductor Nanocrystals (M Y Shen et al.); Excitons on a 1D Periodic Conjugated Polymer Chain: Two Electronic Structures of Polydiacetylene Chains (C Lapersonne-Meyer); Anomalous Spectral Shifts of Indirect Excitons in Coupled GaAs Quantum Wells (D W Snoke et al.); Infrared Absorption by Excitons in Cuprous Oxide (M GAppert et al.); Theory of Excitation-Energy Transfer Processes Involving Optically Forbidden Exciton States in Antenna Systems of Photosynthesis (K Mukai et al.); Transient Grating Induced by Excitonic Polaritons in Thin Film Semiconductors (K Akiyama et al.); Excitonic Photoluminescence of Pentacene Single Crystal (T Aoki-Matsumoto et al.); Scanning Near-Field Optical Microspectroscopy of Single Perylene Microcrystals (J Niitsuma et al.); and other papers. Readership: Condensed matter physicists, materials scientists, chemists and biologists."
Book Synopsis Excitonic Processes In Condensed Matter, Proceedings Of 2000 International Conference (Excon2000) by : Kikuo Cho
Download or read book Excitonic Processes In Condensed Matter, Proceedings Of 2000 International Conference (Excon2000) written by Kikuo Cho and published by World Scientific. This book was released on 2001-08-22 with total page 496 pages. Available in PDF, EPUB and Kindle. Book excerpt: At Yamada Conference LIII, papers on many novel materials and on novel phenomena in condensed matter physics were presented — for instance, the achievement of simultaneous creation of excitons and free-electron-hole pairs in rare gas solids, and a low frequency fluctuation of the spectral shift of indirect excitons in GaAs coupled quantum wells. Single molecule spectroscopy is a powerful tool for studying molecules including biological systems; the study of delocalization of excitons in the photosynthetic light harvesting antenna system was also reported. The proceedings thus contain many excellent papers dealing with current research topics on the excitonic processes in bulk, quantum wells, quantum dots and other confined systems. This book will serve as an excellent source of recent references and reviews for a wide range of researchers in physics, chemistry, engineering and biological sciences.The proceedings have been selected for coverage in:• Index to Scientific & Technical Proceedings (ISTP CDROM version / ISI Proceedings)
Book Synopsis Tableaux anciens des XVIIe-XVIIIe et XIX e siècles objets d'art et de très bel ameublement, tapisseries tapis d'Orient by :
Download or read book Tableaux anciens des XVIIe-XVIIIe et XIX e siècles objets d'art et de très bel ameublement, tapisseries tapis d'Orient written by and published by . This book was released on 1990 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
