Crossover from exciton-polariton to photon Bose-Einstein condensation (original) (raw)
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Exciton-polariton Bose-Einstein condensation: advances and issues
2010
In this review, we present a comprehensive set of experimental results on microcavity-polariton Bose-Einstein Condensation (BEC), obtained within a close collaboration between Institut Neel, Grenoble, France and EPFL, Lausanne, Switzerland. First, we recall the main observations, ie, massive occupation of the ground state and build-up of long range order, which led us to conclude that polariton BEC indeed occurs.
Physical Review B, 2006
It is shown theoretically that Bose condensation of spin-degenerated exciton-polaritons results in spontaneous buildup of the linear polarization in emission spectra of semiconductor microcavities. The linear polarization degree is a good order parameter for the polariton Bose condensation. If spindegeneracy is lifted, an elliptically polarized light is emitted by the polariton condensate. The main axis of the ellipse rotates in time due to self-induced Larmor precession of the polariton condensate pseudospin. The polarization decay time is governed by the dephasing induced by the polaritonpolariton interaction and strongly depends on the statistics of the condensed state. Bose-condensation of exciton-polaritons (polaritons) in microcavities [1] is now in the focus of experimental and theoretical research. Possessing an extremely light effective mass (of the order of 4 10 − m 0 ), polaritons may condense even at room temperature provided that their lifetime is sufficiently long with respect to the characteristic thermalization time [2]. In realistic microcavities, polaritons may have a strongly non-equilibrium distribution in reciprocal space and their condensation is dramatically dependent on their relaxation dynamics. A clear experimental criterion for the condensation has been a subject for debate during recent years [3-4]. Stimulated scattering of polaritons to their ground state,
Experimental evidence for nonequilibrium Bose condensation of exciton polaritons
Physical Review B, 2005
We observe dramatic changes in the near-field and far-field emission from a semiconductor microcavity excited by a pulsed and nonresonant optical pump with varying power. Above a threshold pumping power, light is emitted by a single quantum state lying at the bottom of the lower exciton-polariton band. Its intensity increases exponentially with the pump power and its linewidth becomes narrower than the cavity mode width. Near-field spectroscopy shows that the stimulated emission comes from several bright spots in the cavity plane, but no diffraction-induced angular broadening of the emission is observed. This is direct evidence for spontaneous formation of a nonequilibrium Bose condensate of coherent exciton polaritons with their wave function sharply peaked at structural imperfections.
Bose–Einstein condensation of exciton polaritons
2006
Abstract Phase transitions to quantum condensed phases—such as Bose–Einstein condensation (BEC), superfluidity, and superconductivity—have long fascinated scientists, as they bring pure quantum effects to a macroscopic scale. BEC has, for example, famously been demonstrated in dilute atom gas of rubidium atoms at temperatures below 200 nanokelvin. Much effort has been devoted to finding a solid-state system in which BEC can take place.
Quantized vortices in an exciton–polariton condensate
Nature Physics, 2008
One of the most striking quantum effects in a low temperature interacting Bose gas is superfluidity. First observed in liquid He, this phenomenon has been intensively studied in a variety of systems for its amazing features such as the persistence of superflows and the quantization of the angular momentum of vortices . The achievement of Bose-Einstein condensation (BEC) in dilute atomic gases provided an exceptional opportunity to observe and study superfluidity in an extremely clean and controlled environment. In the solid state, Bose-Einstein condensation of exciton polaritons has now been reported several times. Polaritons are strongly interacting light-matter quasi-particles, naturally occurring in semiconductor microcavities in the strong coupling regime and constitute a very interesting example of composite bosons. Even though pioneering experiments have recently addressed the propagation of a fluid of coherent polaritons , still no conclusive 4 1 2 3,4,5,6 7
Bose-Einstein condensate of cavity exciton polaritons in a trap
JETP Letters, 2011
Consideration of exciton polaritons in an optical microcavity with an embedded quantum well seems promising due to the predicted possibility of the Bose-Einstein condensation (BEC) at high temperatures, up to room temperature . Investigation of such systems is attractive both in view of possible techno logical applications (including the development of an inversion free "polariton laser") and for theoretical and experimental investigations of various aspects of quantum electrodynamics in two dimensions. Despite the short lifetime of exciton polaritons (on the order of picoseconds), a number of experimental indications of the appearance of spontaneous coherence in this sys tem in planar semiconductor microcavities have been recently reported (see, e.g., ).
Bose-Einstein condensation of microcavity polaritons
physica status solidi (b), 2005
The strong coupling of light and excitons in a two-dimensional semiconductor microcavity results in a new eigenstate of quasiparticles called polaritons. Microcavity polaritons have generated much interest due to the wealth of interesting optical phenomena recently observed in these systems such as nonlinear emission, macroscopic coherence, and bosonic stimulated scattering. The efficiency of amplification, parametric oscillation, and coherent emission of