Download or read book Exciton Condensates and Free Carriers in Microcavities and Coupled Quantum Well Structures written by Thomas Taylor and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis examines a series of effects associated with condensation in excitonic systems, and in particular in systems of microcavity exciton-polaritons and indirect excitons. A proposal is presented for a terahertz laser based on a microcavity system, in which a polariton condensate is formed, stimulating the terahertz transition from the 2p exciton state. An associated fundamental effect is predicted, in which the threshold to lasing is dependent on the statistics of the pump photons. The potential of hybrid Bose-Fermi systems for the study of coherent many body phenomena is demonstrated, by modelling the effects of interaction between an excitonic condensate and a two-dimensional electron gas. The fermionic subsystem of electrons is first considered, and it is shown that a phase transition to superconductivity may exist due to pairing mediated by virtual excitations of the condensate, analogous to the phonon mechanism in conventional superconductors. The system is modelled within BCS theory, and the gap equation is solved numerically to yield the critical temperature. The complementary effects of the electron gas on the bosonic condensate are also studied; the effective interaction between the constituents of the condensate may be strongly modified, affecting the superfluid properties of the condensate, and leading to the appearance of a roton minimum in the dispersion of elementary excitations. In fact, the dispersion may be modified to the extent that the roton gap closes, creating an instability in the system - it is shown that this instability may be manifested as a transition to a supersolid phase.

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 2019-06-04 with total page 59 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.

Download or read book Microcavities written by Alexey V. Kavokin and published by Oxford University Press. This book was released on 2017-04-28 with total page 608 pages. Available in PDF, EPUB and Kindle. Book excerpt: Microcavities are semiconductor, metal, or dielectric structures providing optical confinement in one, two or three dimensions. At the end of the 20th century, microcavities have attracted attention due to the discovery of a strong exciton-light coupling regime allowing for the formation of superposition light-matter quasiparticles: exciton-polaritons. In the following century several remarkable effects have been discovered in microcavities, including the Bose-Einstein condensation of exciton-polaritons, polariton lasing, superfluidity, optical spin Hall and spin Meissner effects, amongst other discoveries. Currently, polariton devices exploiting the bosonic stimulation effects at room temperature are being developed by laboratories across the world. This book addresses the physics of microcavities: from classical to quantum optics, from a Boltzmann gas to a superfluid. It provides the theoretical background needed for understanding the complex phenomena in coupled light-matter systems, and it presents a broad overview of experimental progress in the physics of microcavities.

Download or read book Direct Electrical Control of Exciton and Polariton Condensates written by Ming Xie and published by . This book was released on 2017 with total page 198 pages. Available in PDF, EPUB and Kindle. Book excerpt: Excitons are among the most ubiquitous bosonic quasiparticle excitations in solid state systems whose lifetime can be extended such that quasi-thermal equilibrium states can be reached. They have thus been promising subjects for the study of Bose-Einstein condensation (BEC) physics during the last few decades. Indeed, convincing evidence for BEC of excitons and exciton polaritons, which are coupled state of quantum-well excitons and cavity photons, have been reported. In this dissertation, we study the property of two dimensional exciton and exciton-polariton condensates driven by external electric bias and discuss possible electro-optic device applications. In the first chapter, we give a brief introduction to the basic concept of excitons, exciton-polaritons and their condensation, each followed by a short survey of the past and ongoing researches in their respective fields. The second chapter presents our study on the electrically controlled coherent excitonic steady state in two dimensional transition-metal dichalcogenide (TMD) double-layer system. We point out that a pair of electrical contacts with chemical potentials separated by less than the spatially indirect band gap of a 2D double-layer can be used to establish an exciton reservoir with an electrically controlled chemical potential. Equilibration between the exciton fluid and the contacts proceeds via a process involving virtual intermediate states in which an unpaired electron or hole occupies a free carrier state in one of the 2D layers. We relate the equilibration rate between excitons and contacts to the tunneling conductances between the contacts and the individual 2D layers when the contact chemical potentials align with the free-carrier bands. As an initial exploration of how spatially indirect 2D exciton systems can be studied and manipulated electrically, we explain how dc and ac voltage variation can be used to measure thermodynamic properties of the exciton fluid and to characterize the strength of its coupling to the reservoir. In the third chapter, we study the thermo-electric transport properties of excitons. Based on the two-particle tunneling process discussed in previous chapter, we propose a possible realization of a thermo-electric cooling device in which indirect excitons act as the heat carriers. Excitons are injected from the cold side of the device and flow downhill a chemical potential gradient, which is maintained by the bias voltage difference set up between the cold and the hot side, to the hot side where they break into individual electrons and holes exiting to the electrodes. In the fourth chapter, we present a theory of exciton or exciton-polariton supercurrent generation. We describe a mechanism by which an electrical bias voltage applied across a unipolar semiconductor quantum well can drive an exciton or polariton supercurrent. The mechanism depends on the properties of electronic quasiparticles in quantum wells or two-dimensional materials when they are dressed by interactions with the coherent exciton field of an exciton condensate or the coherent exciton and photon fields of a polariton condensate, and on approximate conservation of the sum of the total photon and exciton numbers. We propose experiments that can be performed to realize this new light-matter coupling effect, and discuss possible applications. Assuming the dominant process for electron transfer between conduction and valence bands is by scattering off the condensate, electrical bias voltages can be used to control the condensate. We study the in-plane transport properties of electrical current through the unipolar system, and show how the coherent condensate fields respond to the current flow. The possibility of tailoring light via electrical current and vice versa simultaneously might lead to interesting new applications

Download or read book Semiconductor Photonics of Nanomaterials and Quantum Structures written by Arash Rahimi-Iman and published by Springer Nature. This book was released on 2021-04-23 with total page 288 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book introduces the wider field of functional nanomaterials sciences, with a strong emphasis on semiconductor photonics. Whether you are studying photonic quantum devices or just interested in semiconductor nanomaterials and their benefits for optoelectronic applications, this book offers you a pedagogical overview of the relevant subjects along with topical reviews. The book discusses different yet complementary studies in the context of ongoing international research efforts, delivering examples from both fundamental and applied research to a broad readership. In addition, a hand-full of useful optical techniques for the characterization of semiconductor quantum structures and materials are addressed. Moreover, nanostructuring methods for the production of low-dimensional systems, which exhibit advantageous properties predominantly due to quantum effects, are summarized. Science and engineering professionals in the interdisciplinary domains of nanotechnology, photonics, materials sciences, and quantum physics can familiarize themselves with selected highlights with eyes towards photonic applications in the fields of two-dimensional materials research, light–matter interactions, and quantum technologies.

Download or read book Microcavities written by Alexey Kavokin and published by Oxford University Press, USA. This book was released on 2007-12-20 with total page 486 pages. Available in PDF, EPUB and Kindle. Book excerpt: This is the first book to cover a new and rapidly developing research field in physics. Confining light in small structures called microcavities produces new devices which exploit the quantum physics of light matter interactions.

Download or read book Excitons in Coupled Double Quantum Wells written by Sang Yup Kim and published by . This book was released on 2001 with total page 312 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Microcavities written by Alexey Kavokin and published by Oxford University Press. This book was released on 2011-04-28 with total page 487 pages. Available in PDF, EPUB and Kindle. Book excerpt: This is the first book to cover a new and rapidly developing research field in physics. Confining light in small structures called microcavities produces new devices which exploit the quantum physics of light matter interactions.

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.

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:

Download or read book The Physics of Semiconductor Microcavities written by Benoit Deveaud and published by John Wiley & Sons. This book was released on 2007-02-06 with total page 336 pages. Available in PDF, EPUB and Kindle. Book excerpt: Electron and photon confinement in semiconductor nanostructures is one of the most active areas in solid state research. Written by leading experts in solid state physics, this book provides both a comprehensive review as well as a excellent introduction to fundamental and applied aspects of light-matter coupling in microcavities. Topics covered include parametric amplification and polariton liquids, quantum fluid and non-linear dynamical effects and parametric instabilities, polariton squeezing, Bose-Einstein condensation of microcavity polaritons, spin dynamics of exciton-polaritons, polariton correlation produced by parametric scattering, progress in III-nitride distributed Bragg reflectors using AlInN/GaN materials, high efficiency planar MCLEDs, exciton-polaritons and nanoscale cavities in photonic crystals, and MBE growth of high finesse microcavities.

Download or read book Polariton Physics written by Arash Rahimi-Iman and published by Springer Nature. This book was released on 2020-03-05 with total page 291 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book offers an overview of polariton Bose–Einstein condensation and the emerging field of polaritonics, providing insights into the necessary theoretical basics, technological aspects and experimental studies in this fascinating field of science. Following a summary of theoretical considerations, it guides readers through the rich physics of polariton systems, shedding light on the concept of the polariton laser, polariton microcavities, and the technical realization of optoelectronic devices with polaritonic emissions, before discussing the role of external fields used for the manipulation and control of exciton–polaritons. A glossary provides simplified summaries of the most frequently discussed topics, allowing readers to quickly familiarize themselves with the content. The book pursues an uncomplicated and intuitive approach to the topics covered, while also providing a brief outlook on current and future work. Its straightforward content will make it accessible to a broad readership, ranging from research fellows, lecturers and students to interested science and engineering professionals in the interdisciplinary domains of nanotechnology, photonics, materials sciences and quantum physics.

Download or read book Cavity Polaritons written by Alexey Kavokin and published by Elsevier. This book was released on 2003-11-26 with total page 248 pages. Available in PDF, EPUB and Kindle. Book excerpt: Volume 32 of the series addresses one of the most rapidly developing research fields in physics: microcavities. Microcavities form a base for fabrication of opto-electronic devices of XXI century, in particular polariton lasers based on a new physical principle with respect to conventional lasers proposed by Einstein in 1917. This book overviews a theory of all major phenomena linked microcavities and exciton-polaritons and is oriented to the reader having no background in solid state theory as well as to the advanced readers interested in theory of exciton-polaritons in microcavities. All major experimental discoveries in the field are addressed as well. · The book is oriented to a general reader and is easy to read for a non-specialist.· Contains an overview of the most essential effects in physics of microcavities experimentally observed and theoretically predicted during the recent decade such as:. · Bose-Einstein condensation at room temperature.· Lasers without inversion of population.· Microcavity boom: optics of the XXI century!· Frequently asked questions on microcavities and responses without formulas. · Half-light-half-matter quasi-particles: base for the future optoelectronic devices

Download or read book Electron and Photon Confinement in Semiconductor Nanostructures written by Benoît Deveaud and published by IOS Press. This book was released on 2003 with total page 584 pages. Available in PDF, EPUB and Kindle. Book excerpt: The purpose of this course was to give an overview of the physics of artificial semiconductor structures confining electrons and photons. It furnishes the background for several applications in particular in the domain of optical devices, lasers, light emitting diodes or photonic crystals. The effects related to the microactivity polaritons, which are mixed electromagnetic radiation-exciton states inside a semiconconductor microactivity are covered. The study of the characteristics of such states shows strong relations with the domain of cavity quantum electrodynamics and thus with the investigation of some fundamental theoretical concepts.

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.

Download or read book Strong Light matter Coupling in Microcavity embedded Semiconductor Quantum Wells and Quantum Dots written by Kanchana Sivalertporn and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis presents a theoretical investigation of exciton polaritons in strongly-coupled exciton-photon microcavity systems. Two different systems, a coupled quantum well (CQW) embedded in a planar microcavity and a quantum dot (QD) inside a micropillar cavity, are studied using suitable theoretical models. The exciton-polariton states are calculated and their optical properties are investigated in detail, showing a good agreement with experimental observations. For a CQW structure, the excitonic states in the presence of the electric field applied in the growth direction are calculated by solving the Schrodinger equation in real space. The field dependence of exciton transition energy, binding energy, oscillator strength, lifetime and absorption is studied. The exciton ground state experiences a crossover from direct to indirect state at low electric field. A single state-basis calculation in which only the electron and hole ground states are taken into account is also made and compared with the full accurate calculation model. The polariton effect in a microcavity-embedded CQW is investigated based on the semiclassical theory. The light-matter interaction is treated by solving coupled material and Maxwell's equations. The reflectivity and absorption spectra are calculated for different detunings using the scattering matrix method. When a cavity mode is tuned to an exciton mode (zero detuning), an anticrossing of two polariton modes is observed, showing that the system is in the strong coupling regime. In addition, the fractions of direct exciton, indirect exciton and cavity modes contributed to the polariton states are calculated using the microscopic theory. The resulting polariton state with comparable contributions ofall three components called dipolariton is observed. Finally, the dynamics of the strongly-coupled exciton-cavity system in the QD-micropillar system is studied using the four wave mixing (FWM) theory applied to the Jaynes-Cummings model. Spectrally resolved and time-resolved FWM signals are calculated for different temperatures. Temperature plays the role of the parameter controlling the detuning. The beat periods of the first and second rungs of the JC ladder are also investigated, showing that the second rung has a sqaure- shorter period compared to the beat period of the first rung. To reveal the coherent coupling between two distant QDs, the FWM signals are Fourier-transformed into a two-dimensional frequency domain. It is found that the off-diagonal components in these 2D spectra are nonzero, demonstrating the coherent coupling between isolated QDs. In addition, the phase correction is developed. This procedure is neccessary for a comparison with the experiment which has random phases for different detunings. A quantitative agreement between the prediction and measurement is achieved and demonstrated.

Download or read book Competition Between Tunneling and Exciton Formation for Photoexcited Carriers in Asymmetric Double Wells written by J. Kuhl and published by . This book was released on 1992 with total page 6 pages. Available in PDF, EPUB and Kindle. Book excerpt: The formation of excitons from photoexcited free carriers in a GaAs asymmetric double quantum well tunneling structure is shown to occur by a bimolecular process. Using the non-linear luminescence cross-correlation technique, a bi-molecular formation coefficient of 6xlO-12cm2/ps is determined. The electron and hole tunneling times are also simultaneously obtained.