DOCSLIB.ORG

Dynamics of Spin Polarization in Tilted Polariton Rings

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Dynamics of Spin Polarization in Tilted Polariton Rings Dynamics of spin polarization in tilted polariton rings S. Mukherjee,1 V. K. Kozin,2, 3 A. V. Nalitov,3, 4, 5 I. A. Shelykh,2, 3 Z. Sun,1, 6 D. M. Myers,1 B. Ozden,1, 7 J. Beaumariage,1 M. Steger,1 L. N. Pfeiffer,8 K. West,8 and D. W. Snoke1 1Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA 15260, USA 2Science Institute, University of Iceland, Dunhagi-3, IS-107 Reykjavik, Iceland 3ITMO University, St. Petersburg 197101, Russia 4Faculty of Science and Engineering, University of Wolverhampton, Wulfruna St, Wolverhampton WV1 1LY, UK 5Institut Pascal, PHOTON-N2, Universit´e Clermont Auvergne, CNRS, SIGMA Clermont, Institut Pascal, F-63000 Clermont-Ferrand, France. 6State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200062, China 7Department of Physics and Engineering, Penn State Abington, Abington, PA 19001, USA 8Department of Electrical Engineering, Princeton University, Princeton, NJ 08544, USA We have observed the effect of pseudo magnetic field originating from the polaritonic analog of spin-orbit coupling (TE−TM splitting) on a polariton condensate in a ring shaped microcavity. The effect gives rise to a stable four-leaf pattern around the ring as seen from the linear polarization measurements of the condensate photoluminescence. This pattern is found to originate from the in- terplay of the cavity potential, energy relaxation and TE-TM splitting in the ring. Our observations are compared to the dissipative one-dimensional spinor Gross-Pitaevskii equation with the TE-TM splitting energy which shows good qualitative agreement. I. INTRODUCTION spin Hall effect is realized by actual transport of po- laritons while the spin of the polaritons precess as they move. Over a decade has passed since the first demon- stration of Bose-Einstein condensation of exciton- In this paper we address how the two spinor com- polaritons in a semiconductor microcavity [1, 2]. It ponents of a gas of highly excited trapped polaritons stands out as a unique platform for exploring physics evolve following a quench in a long lifetime (≈ 200 of out of equilibrium systems. Recent reports on the ps) microcavity. The trapping potential is created observation of thermal equilibration [3, 4] on one by patterning the top mirror of the GaAs microcav- hand have triggered interest in studying equilibrium ity in the shape of a ring. The polaritons in the physics in non-hermitian systems, while on the other ring maintain the same long lifetime (≈ 200 ps), have shown promise for making devices based on po- high quality (Q > 105) and low disorder as in the lariton condensates which operate near equilibrium. two-dimensional planar microcavity used previously Such a feat been achieved in microcavities with Q [3, 5, 11{13]. With the presence of a unidirectional > 105, allowing several collision events between po- gradient in the energy of the polaritons, the circular laritons to distribute energy and thermalize in their symmetry of the ring is broken, giving rise to a rigid lifetime [3{6]. rotor potential. Combined with a momentum depen- These systems also naturally offer a way for de- dent effective magnetic field in the trap, this results scribing a pseudo-spin 1/2 Bose gas [7]. The order in intrinsic optical spin Hall effect as the polaritons parameter of a polariton condensate is described by are transported to the region with the lowest energy a two-component complex valued spinor, which is in the trap. We map the spin of the condensed po- connected to the electric polarization of the polari- laritons in the ring using space- and time- resolved tons in the microcavity [8]. In the presence of a spin-polarized spectroscopy. non-aligned magnetic field the spin of the polaritons The rings are fabricated by etching the top dis- is precessing similarly to the spin of an electron in tributed Bragg reflector (DBR) of this microcavity a magnetic field. It turns out that for a quantum in the shape of rings of width (the difference of the well embedded inside a semiconductor microcavity, outer and the inner radii) 15 µm and radius (aver- a small but non-negligible momentum dependent ef- age of outer and inner radii) 50 µm. Further details fective magnetic field is present which lies in the may be found in the previous papers [13{15]. Across plane of the quantum well. This has been used to the typical dimensions of the ring, the thickness of realize a polaritonic analog of extrinsic [9] as well as the microcavity varies which leads to a cavity energy intrinsic [10] spin Hall effect. In contrast to the elec- gradient (≈ 7−9 meV/mm). The cavity gradient ef- tronic systems where the spin Hall effect gives rise fect is similar to an artificial gravity for the polari- to a spin current and no mass transport, the optical tons making the rings look tilted on the potential 2 energy plane. Due to the analogy to gravity, here The rate of energy drop of the polaritons measures we will refer to the point of highest potential energy the rate at which the exciton cloud decays. By the as the \top" of the ring, and the point of lower po- time the polaritons arrive at the bottom of the ring tential energy, on the opposite side of the ring, as trap it has already undergone considerable energy re- the \bottom". The effect of the artificial gravity on laxation (≈ 2 meV). The energy- and time- resolved the spin-polarized polaritons have been theoretically image from the bottom in Fig. 2 (c) shows that as studied in Ref. [16]. the occupation density of the polaritons increases, the spectral linewidth of the emission narrows indi- cating build up of coherence in the bottom of the II. EXPERIMENT trap. We have combined the streak images from the top and bottom of the ring for comparison in Fig. 2 (c). In Fig. 2 (a) and (b) we show spatially and tem- The top of the rings are non-resonantly pumped porally resolved energy and linewidth of the emission (Epump ≈ 1710 meV which is at least 100 meV from the full ring. From these plots we infer that the higher than the energy of the lower branch polari- spatial coherence extends at most to one-third of the tons at the point of excitation) with a mode-locked ring circumference at any given point in time, which Ti:sapphire laser with a pulse repetition rate of 76 is signaled by the energy locking of the emission. At MHz, a pulse width of ≈ 2 ps, a spot size of ≈ 15 µm ◦ late times the energy of the emission approaches the on the sample and incident at an angle of ≈ 45 from local, low density kjj = 0 lower polariton energy. the plane of the sample with more than 90% linear polarization. Due to the high angle injection, the We resolved the polarization of the PL from the pump spot is not circular on the plane of the sam- ring by performing a full Stokes vector measurement ple and creates asymmetry in the direction of the (S0, S1, S2, S3) using combinations of half or quar- polaritons streaming from the pump spot. Photolu- ter waveplate and a linear polarizer. The measure- minescence (PL) from the rings was collected using ment was done on the collimated signal just after the a microscope objective with a numerical aperture microscope objective. The transmission axis of the (NA) of 0.40 and imaged onto the entrance slit of polarizer was chosen to be vertical in the lab frame a spectrometer. The image was then sent through and was kept fixed throughout the experiment. This the spectrometer either to a standard charged cou- was done to remove the polarization sensitivity of pled device (CCD) chip located at one of the exit the optics downstream in the setup. We used an- ports of the spectrometer for time integrated imag- other half waveplate and a polarizer before the en- ing, or onto a Hamamatsu streak camera located trance slit of the spectrometer to collect all the signal at the other exit port for time-resolved imaging. which didn't get reflected, scattered or absorbed af- All measurements were performed by cooling the ter passing through the optics. For all the measure- microcavity to low temperature (below 10 K) in a ments the orientation of the transmission axis of the continuous-flow cold-finger cryostat. A sketch of the final polarizer was also kept fixed, which removed experimental setup is shown in Fig. 1. the polarization sensitivity of all the optics inside the spectrometer as the light that entered the spec- The non-resonant optical pulse excites a popula- trometer was always at a fixed linear polarization. tion of free electrons and holes at the top of the ring Two images were taken for each individual measure- which undergo rapid thermalization, turning into ex- ment, one with the half waveplate fast axis (placed citons. Excitons further relax down in energy and ◦ just before the final polarizer) at 0 and one with it reach the anti-crossing spectral region of the pho- ◦ at 45 . By adding these two images together, the tonic and excitonic dispersion branches, forming a total contribution of both polarizations (both paral- dense polariton gas (see, for example, Tassone et lel and orthogonal to the final polarizer) were taken al. [17]), which above a critical density undergoes into account. Additional details on the full Stokes non-equilibrium Bose-Einstein condensation. This vector measurement are given in Appendix B. non-equilibrium condensate streams out ballistically from the excitation spot and fills the entire ring, Time-resolved Stokes vector measurements were while also dropping in energy as it moves in the done using the streak camera.
Load more

Recommended publications
  • Predicting the Ionization Threshold for Carriers in Excited Semiconductors
    Predicting the Ionization Threshold for Carriers in Excited Semiconductors David Snoke Department of Physics and Astronomy University of Pittsburgh, Pittsburgh, PA 15260 Abstract A simple set of formulas is presented which allows prediction of the fraction of ionized carriers in an electron-hole-exciton gas in a photoexcited semiconductor. These results are related to recent experiments with excitons in single and double quantum wells. Many researchers in semiconductor physics talk of \the" Mott transition density in a system of excitons and electron-hole plasma, but do not have a clear handle on exactly how to predict that density as a function of temperature and material parameters in a given system. While numerical studies have been performed for the fraction of free carriers as a function of carrier density and temperature [1, 2], these do not give a readily-accessible intuition for the transition. In this paper I present a simple approach which does not involve heavy numerical methods, but is still fairly realistic. The theory is based on two well-known approximations, which are the mass- action equation for equilibrium in when different species can form bound states, and the static (Debye) screening approximation. In addition, simple approximations are used for numerical calculations of the excitonic Rydberg as a function of screening length. 1 Two \Mott" transitions The first issue to deal with is what Mott transition we are concerned with. There are arXiv:0709.1415v1 [cond-mat.other] 10 Sep 2007 actually two very different conductor-insulator transitions which go under the name of the \Mott" transition. The first, originally envisioned by Mott, occurs when the wave function overlap of bound states increases to the point that banding occurs.
    [Show full text]
  • Polariton Condensation and Lasing
    Polariton Condensation and Lasing David Snoke Department of Physics and Astronomy University of Pittsburgh, Pittsburgh, PA 15260, USA Abstract The similarities and differences between polariton condensation in mi- crocavities and standard lasing in a semiconductor cavity structure are reviewed. The recent experiments on \photon condensation" are also re- viewed. Polariton condensation and lasing in a semiconductor vertical-cavity, surface- emitting laser (VCSEL) have many properties in common. Both emit coherent light normal to the plane of the cavity, both have an excitation density threshold above which there is optical gain, and both can have in-plane coherence and spontaneous polarization. Is there, then, any real difference between them? Should we drop the terminology of Bose-Einstein condensation (BEC) altogether and only talk of polariton lasing? The best way to think of this is to view polariton condensation and standard lasing as two points on a continuum, just as Bose-Einstein pair condensation and Bardeen-Cooper-Schreiffer (BCS) superconductivity are two points on a continuum. In the BEC-BCS continuum, the parameter which is varied is the ratio of the pair correlation length to the average distance between the under- lying fermions; BEC occurs when the pair correlation length, i.e., the size of a bound pair, is small compared to the distance between particles, while BCS superconductivity (which has the same mathematics as the excitonic insulator (EI) state, in the case of neutral electron-hole pairs) occurs when the pair cor-
    [Show full text]
  • The New Era of Polariton Condensates David W
    The new era of polariton condensates David W. Snoke, and Jonathan Keeling Citation: Physics Today 70, 10, 54 (2017); doi: 10.1063/PT.3.3729 View online: https://doi.org/10.1063/PT.3.3729 View Table of Contents: http://physicstoday.scitation.org/toc/pto/70/10 Published by the American Institute of Physics Articles you may be interested in Ultraperipheral nuclear collisions Physics Today 70, 40 (2017); 10.1063/PT.3.3727 Death and succession among Finland’s nuclear waste experts Physics Today 70, 48 (2017); 10.1063/PT.3.3728 Taking the measure of water’s whirl Physics Today 70, 20 (2017); 10.1063/PT.3.3716 Microscopy without lenses Physics Today 70, 50 (2017); 10.1063/PT.3.3693 The relentless pursuit of hypersonic flight Physics Today 70, 30 (2017); 10.1063/PT.3.3762 Difficult decisions Physics Today 70, 8 (2017); 10.1063/PT.3.3706 David Snoke is a professor of physics and astronomy at the University of Pittsburgh in Pennsylvania. Jonathan Keeling is a reader in theoretical condensed-matter physics at the University of St Andrews in Scotland. The new era of POLARITON CONDENSATES David W. Snoke and Jonathan Keeling Quasiparticles of light and matter may be our best hope for harnessing the strange effects of quantum condensation and superfluidity in everyday applications. magine, if you will, a collection of many photons. Now and applied—remains to turn those ideas into practical technologies. But the dream imagine that they have mass, repulsive interactions, and isn’t as distant as it once seemed. number conservation.
    [Show full text]
  • Scientists Dissent List
    A SCIENTIFIC DISSENT FROM DARWINISM “We are skeptical of claims for the ability of random mutation and natural selection to account for the complexity of life. Careful examination of the evidence for Darwinian theory should be encouraged.” This was last publicly updated April 2020. Scientists listed by doctoral degree or current position. Philip Skell* Emeritus, Evan Pugh Prof. of Chemistry, Pennsylvania State University Member of the National Academy of Sciences Lyle H. Jensen* Professor Emeritus, Dept. of Biological Structure & Dept. of Biochemistry University of Washington, Fellow AAAS Maciej Giertych Full Professor, Institute of Dendrology Polish Academy of Sciences Lev Beloussov Prof. of Embryology, Honorary Prof., Moscow State University Member, Russian Academy of Natural Sciences Eugene Buff Ph.D. Genetics Institute of Developmental Biology, Russian Academy of Sciences Emil Palecek Prof. of Molecular Biology, Masaryk University; Leading Scientist Inst. of Biophysics, Academy of Sci., Czech Republic K. Mosto Onuoha Shell Professor of Geology & Deputy Vice-Chancellor, Univ. of Nigeria Fellow, Nigerian Academy of Science Ferenc Jeszenszky Former Head of the Center of Research Groups Hungarian Academy of Sciences M.M. Ninan Former President Hindustan Academy of Science, Bangalore University (India) Denis Fesenko Junior Research Fellow, Engelhardt Institute of Molecular Biology Russian Academy of Sciences (Russia) Sergey I. Vdovenko Senior Research Assistant, Department of Fine Organic Synthesis Institute of Bioorganic Chemistry and Petrochemistry Ukrainian National Academy of Sciences (Ukraine) Henry Schaefer Director, Center for Computational Quantum Chemistry University of Georgia Paul Ashby Ph.D. Chemistry Harvard University Israel Hanukoglu Professor of Biochemistry and Molecular Biology Chairman The College of Judea and Samaria (Israel) Alan Linton Emeritus Professor of Bacteriology University of Bristol (UK) Dean Kenyon Emeritus Professor of Biology San Francisco State University David W.
    [Show full text]
  • Introduction to Apologetics-Part IV
    Introduction to Apologetics-Part IV Course modeled after Frank Turek and Norman Geisler’s I Don’t Have Enough Faith to Be an Atheist curriculum, with additional materials from William Lane Craig, J.P. Moreland, Hugh Ross, Stephen Meyers, John Lennox, Douglas Groothuis, N.T. Wright, Ravi Zacharias, Andy Bannister, Paul Copan, and Rodney Stark. Course Outline: I. The Four Questions Everybody Needs to Ask of Their Belief System II. Can You Handle the Truth? III. The Big Bang of Science and Theology IV. Watchmaker, Watchmaker, Make Me a Watch V. The Herd and the Gut VI. All We Need is a Miracle VII. Can Somebody Give Me a Testimony? VIII. Books of Myth or Books of Truth? IX. Who is This Jesus Guy? X. The One Answer to the Four Questions Can You Handle the Truth? 1. Truth about reality is knowable. 2. The opposite of true is false. 3. It is true that the theistic God exists. 4. If God exists, then miracles are possible. 5. Miracles can be used to confirm a message from God. 6. The New Testament is historically reliable. 7. The New Testament says Jesus claimed to be God. 8. Jesus’ claim to be God was miraculously confirmed by His fulfillment of prophecies, His sinless life and miraculous deeds, and His prediction and accomplishment of His resurrection. 9. Therefore, Jesus is God. 10. Whatever Jesus (who is God) teaches is true. 11. Jesus taught that the Bible is the Word of God. 12. Therefore, it is true that the Bible is the Word of God (and anything opposed to it is false).
    [Show full text]
  • In Favor of God-Of-The-Gaps Reasoning
    In Favor of God-of-the-Gaps Reasoning David Snoke * Department of Physics and Astronomy snoke @pitt .edu University of Pittsburgh Pittsburgh, PA 15260 It is passe to reject “God-of-the-gaps” arguments, but I argue that it is perfectly reasonable to argue against atheism based on its lack of explanatory power. The standard argument against God-of-the-gaps reasoning deviates from the mode of normal scientific discourse, it assumes a view of history which is incorrect, and it tacitly implies a naive optimism about the abilities of science. I encourage apologists to point out gaps of explanation in atheistic theories wherever they see them, and expect atheists to return the favor. For more than fif teen years, I have read the ASA Three Objections to jour nal and par tic i pated in dis cus sions of sci ence and Chris tian ity. Dur ing this time, I have found that Anti-God-of-the-Gaps Arguments while ASA mem bers dis agree over many things, 1. Nor mal Rules of Evi den tial Dis course cer tain unques tioned points of agree ment flow On the sur face, the AGOG posi tion seems strange through all of our dis cus sions. In par tic u lar, I have when viewed from the per spec tive of nor mal sci en- found that no mat ter what the topic, one com mon tific dis course. In decid ing between two com pet ing prem ise seems to reign supreme. This is the uni ver- the o ries, we are told at the out set that we must not 1 sal con dem na tion of God-of-the-gaps argu ments.
    [Show full text]
  • Abstract Submitted for the MAR13 Meeting of the American Physical Society
    Abstract Submitted for the MAR13 Meeting of The American Physical Society Coherent flow and Bose-Einstein Condensation of Long Lifetime Polaritons1 GANGQIANG LIU, BRYAN NELSON, MARK STEGER, Depart- ment of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA 15260, RYAN BALILI, Department of Physics, MSU-Iligan Insititute of Technology, Iligan, 9200, Philippines, DAVID SNOKE, Department of Physics and Astronomy, Uni- versity of Pittsburgh, Pittsburgh, PA 15260, KEN WEST, LOREN PFEIFFER, Department of Electrical Engineering, Princeton University, NJ 08544, USA | Exciton-polaritons with lifetimes of the order of 100ps are created in semiconductor microcavity of extremely high quality factor (? 106). Due to this long lifetime and very few defects in the sample, the polaritons can travel ballistically over macroscopic distances up to millimeter. The properties of the system changes dramatically with the particle density. At moderate density, the polaritons behave like a superfluid, maintaining phase coherence after propagating over hundreds of microns. This in- dicates the existence of long range spatial coherence in the system. As the density increases above a threshold value, the polaritons condense into the lowest-energy state of the effective trap produced by the repulsive interaction between the polari- tons and excitons within the excitation region and the cavity gradient across the sample. The coherence time of this polariton BEC is measured to be at least 280ps. By creating a exciton barrier at the center of a stress trap, we are able to obtain a ring shape polariton BEC which provides the opportunity for studying the constant flow of a superfluid in the polariton system. 1This work is support by National Science Foundation under grant DMR-1104383, Gordon and Betty Moore Foundation as well as the National Science Foundation MRSEC Program through the Princeton Center for Complex Materials (DMR- 0819860).
    [Show full text]
  • Bibliographic and Annotated List of Peer-Reviewed Publications Supporting Intelligent Design
    BIBLIOGRAPHIC AND ANNOTATED LIST OF PEER-REVIEWED PUBLICATIONS SUPPORTING INTELLIGENT DESIGN UPDATED JULY, 2017 PART I: INTRODUCTION While intelligent design (ID) research is a new scientific field, recent years have been a period of encouraging growth, producing a strong record of peer-reviewed scientific publications. In 2011, the ID movement counted its 50th peer-reviewed scientific paper and new publications continue to appear. As of 2015, the peer-reviewed scientific publication count had reached 90. Many of these papers are recent, published since 2004, when Discovery Institute senior fellow Stephen Meyer published a groundbreaking paper advocating ID in the journal Proceedings of the Biological Society of Washington. There are multiple hubs of ID-related research. Biologic Institute, led by molecular biologist Doug Axe, is “developing and testing the scientific case for intelligent design in biology.” Biologic conducts laboratory and theoretical research on the origin and role of information in biology, the fine-tuning of the universe for life, and methods of detecting design in nature. Another ID research group is the Evolutionary Informatics Lab, founded by senior Discovery Institute fellow William Dembski along with Robert Marks, Distinguished Professor of Electrical and Computer Engineering at Baylor University. Their lab has attracted graduate-student researchers and published multiple peer-reviewed articles in technical science and engineering journals showing that computer programming “points to the need for an ultimate information source qua intelligent designer.” Other pro-ID scientists around the world are publishing peer-reviewed pro-ID scientific papers. These include biologist Ralph Seelke at the University of Wisconsin Superior, Wolf-Ekkehard Lönnig who recently retired from the Max Planck Institute for Plant Breeding Research in Germany, and Lehigh University biochemist Michael Behe.
    [Show full text]
  • A Lawyer's Take on Darwin Devolves
    A Lawyer’s Take on Michael Behe’s Latest Book, Darwin Devolves: The New Science about DNA that Challenges Evolution By John Calvert May 6, 2019 I’ve known Dr. Behe for the last 20 years. We met when I switched my legal specialty from stock fraud to the Constitutional rights of parents and students in K-12 public education. I’m also a geologist and former “Secular” Humanist who has no qualms with an old age of the Earth. I buried my former materialistic view of life after I read an article 40 years ago about how DNA uses a code to store the functionally complex information that accounts for the origin, development and operation of living systems. It struck me that the genetic code resembles the Morse code, developed by the mind of Samuel Morse. Both use a set of symbols to convert information into something else. For the Morse code the something else is words, numbers and punctuation marks. For the genetic code the something else are strings of amino acids that fold into integrated proteins that make, repair, regulate and replicate life. I didn’t see how physics, chemistry and chance alone could explain the code or its incomprehensibly sophisticated coded “messages” that define life. So, in 1982 I began a somewhat haphazard research project about how science accounts for the origin of life and its diversity. In that search I learned that modern evolutionary theory – origins science – is based on a doctrine that does not permit consideration of the idea that the kind of foresight necessary to make the Morse code might be needed to construct the genetic code.
    [Show full text]
  • An Introduction to Intelligent Design
    An Introduction to Intelligent Design © Dr Arthur Jones Contents Introduction 2 Defining ID 2 Three Areas of Design 2 The Physical Universe 3 Living Organisms 3 Science and Technology 4 Information 4 Beyond the Reach of Chance 5 Evolution and Materialism 6 The Religious Root of Evolution 7 Evolution as Religion 9 Naturalism and Evolution as a Defeater for Science and Reason 10 The Two Foundational Laws of Biology 11 The Law of Biogenesis 11 The Law of Heredity 11 There is Much More to Heredity thanDNA 12 References 13 Bibliography 16 Worldviews 16 Intelligent Design 16 General 16 Textbooks 18 God of the Gaps? 18 Intelligent Design DVDs 18 Some Intelligent Design Websites 18 Failure of Naturalism 19 DNA is Only Part of Heredity 19 Author Information 20 Appendices – Other Relevant Matters 21 A Extrinsic and Intrinsic ID 21 B Core and Peripheral Beliefs 21 C Naturalism and Materialism 22 D Method, Realism and Completeness 22 E Paradigm Shifts 23 F The Bush of Knowledge 24 References 24 02/2013 -Page 1- Dr Arthur Jones – An Introduction to ID Page 2 of 25 Introduction “Any story sounds true until someone tells the other side and sets the record straight.” (Proverbs 18: 7, LB) When interrogating the diverse positions on origins, it is essential that real cultural watersheds are recognised and real positions addressed, not imaginary ones that play little or no role in the thinking of the scholars in question. When a sophisticated, adult version of our favoured position is played off against ‘Noddy’ versions of other positions, the outcome is assured, but furthers neither the debate, nor the search for truth.
    [Show full text]
  • New Possibilities with Long-Lifetime Microcavity Polaritons
    New possibilities with long-lifetime microcavity polaritons David Snoke University of Pittsburgh Experimental collaborators: R. Balili, G. Liu, B. Nelsen, M. Steger, U. Pittsburgh L. Pfeiffer, K. West, Princeton U. P. Wen, Y. Sun, K. Nelson, MIT A. Hayat, H. van Driel, A. Steinberg, U. Toronto Theory collaborators: A. Daley, Strathclyde U. A. MacDonald, U. Texas Austin Steve Girvin, Yale U. H. Tureci, Princeton U. Supported by the NSF under Grant DMR-1104383 and ARO Grant W911-NF-15-1-0466. Strong coupling in a cavity solid: maximum density of oscillators coupling energy = g N where N is the number of atoms tradeoff: disorder 2 2 2 2 cavity photon: E c kz k|| c ( / L) k|| uppercavity polariton photon exciton exciton lower polariton Mixing leads to “upper polariton” (UP) and “lower polariton” (LP) -4 LP effective mass ~ 10 me Polariton properties vs. detuning For LP, = photon fraction, = exciton fraction. 4 A thought experiment: external loading of trap continuous tunneling out of ground state θ Bragg scattering measurement gives A(k,ω) This is exactly how cavity polariton (“heavy photon”) condensates are monitored: photons in (pumping), equilibration, tunneling out through the mirrors, spectroscopy. Lifetime of microcavity polariton systems leakage out of mirrors: intrinsic cavity photon lifetime early samples: ~ 1 ps Baumberg, Bloch: ~ 10 ps Snoke/Pfeiffer: 135 ps Polariton lifetime is longer than this: Twice the photon lifetime at resonance. ∞ in excitonic limit. Typical experiment: collisional thermalization time ~ 5-10 ps In new samples, lifetime is ~ 300 ps. Angle-resolved photon emission data give momentum distribution We can therefore k k z image the gas in both real space and momentum space as data.
    [Show full text]
  • Excitons at High Density in Cuprous Oxide and Coupled Quantum Wells
    View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by D-Scholarship@Pitt EXCITONS AT HIGH DENSITY IN CUPROUS OXIDE AND COUPLED QUANTUM WELLS by Yingmei Liu B. S., JiLin University, 1996 M. S., JiLin University, 1999 M. S., University of Pittsburgh, 2000 Submitted to the Graduate Faculty of the Faculty and college of Arts and Sciences in partial fulfillment of the requirements for the degree of Doctor of Philosophy University of Pittsburgh 2004 UNIVERSITY OF PITTSBURGH FACULTY AND COLLEGE OF ARTS AND SCIENCES This dissertation was presented by Yingmei Liu It was defended on July 22th 2004 and approved by David W. Snoke, Department of Physics and Astronomy Daniel Boyanovsky, Department of Physics and Astronomy Robert P. Devaty, Department of Physics and Astronomy Gilbert Walker, Department of Chemistry Xiao-lun Wu, Department of Physics and Astronomy Dissertation Director: David W. Snoke, Department of Physics and Astronomy ii Advisor: David Wayne Snoke EXCITONS AT HIGH DENSITY IN CUPROUS OXIDE AND COUPLED QUANTUM WELLS Yingmei Liu, PhD University of Pittsburgh, 2004 There is a 40-year long history in the search for Bose-Einstein condensation (BEC) of excitons in semiconductors. This thesis presents research directed toward this goal in bulk crystal Cu2O in three dimensions and in GaAs-based coupled quantum wells (CQW) in two dimensions. The Auger recombination process in Cu2O plays a major role in limiting the density of the excitons. We find that the rate for this process increases with applied stress and lattice temperature. We create paraexcitons in Cu2O through a resonant two-photon excitation in a harmonic potential trap with the Auger recombination process as small as possible (at low temperature and low stress), and find that the exciton creation efficiency in the resonant two-photon excitation is greater for one-beam excitation than for two colliding pulses, but the colliding pulse method may be useful for direct creation of a condensate in the ground state.
    [Show full text]