Electron-Polariton Scattering in Semiconductor Microcavities

Lagoudakis, Pavlos G.; Martin, M. D.; Baumberg, Jeremy J.; Qarry, A.; Cohen, E.; Pfeiffer, L. N.

doi:10.1103/physrevlett.90.206401

Cited by 60 publications

(39 citation statements)

References 22 publications

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“…These states act as a reservoir from which polaritons relax into the confined states at lower energy. The relaxation can take place through interaction with the thermal bath of phonons, 26 with free carriers, 27 or via mutual polariton interaction. 28 The broken translational symmetry of the confined system lifts the constraint of momentum conservation, thus enhancing the relaxation efficiency compared to the case of a planar microcavity.…”

Section: Discussionmentioning

confidence: 99%

Engineering the spatial confinement of exciton polaritons in semiconductors

et al. 2006

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We demonstrate three-dimensional spatial confinement of exciton-polaritons in a semiconductor microcavity. Polaritons are confined within a micron-sized region of slightly larger cavity thickness, called mesa, through lateral trapping of their photon component. This results in a shallow potential well that allows the simultaneous existence of extended states above the barrier. Photoluminescence spectra were measured as a function of either the emission angle or the position on the sample. Striking signatures of confined states of lower and upper polaritons, together with the corresponding extended states at higher energy, were found. In particular, the confined states appear only within the mesa region, and are characterized by a discrete energy spectrum and a broad angular pattern. A theoretical model of polariton states, based on a realistic description of the confined photon modes, supports our observations.

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Section: Discussionmentioning

confidence: 99%

Engineering the spatial confinement of exciton polaritons in semiconductors

et al. 2006

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“…Exciton-polaritons are electrically neutral and cannot carry electric current. However, they may coexist and interact with free electrons or holes, if these carriers are introduced in the same QW with the excitons or in a neighboring QW [9]. When confined together, exciton-polaritons and free carriers form a BoseFermi mixture which is expected to exhibit peculiar optical and electronic properties.…”

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Exciton-Polariton Mediated Superconductivity

2010

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We revisit the exciton mechanism of superconductivity in the framework of microcavity physics, replacing virtual excitons as a binding agent of Cooper pairs by excitations of an exciton-polariton Bose-Einstein condensate. We consider a model microcavity where a quantum well with a two dimensional electron gas is sandwiched between two undoped quantum wells, where a polariton condensate is formed. We show that the critical temperature for superconductivity dramatically increases with the condensate population, opening a new route towards high temperature superconductivity. [5,6]. Their in-plane dispersion is strongly nonparabolic. Near the ground state corresponding to zero in-plane wavevector, an extremely small polariton mass-averaging the exciton mass and the much smaller cavity-photon mass-brings the critical temperature for quantum degeneracy up to room temperature [7,8]. On the other hand, at wavevectors exceeding the wavevector of light at the exciton resonance frequency, the polariton dispersion becomes exciton-like and its effective mass exceeds that near the band minimum by four orders of magnitude (see Fig. 1). Exciton-polaritons are electrically neutral and cannot carry electric current. However, they may coexist and interact with free electrons or holes, if these carriers are introduced in the same QW with the excitons or in a neighboring QW [9]. When confined together, exciton-polaritons and free carriers form a BoseFermi mixture which is expected to exhibit peculiar optical and electronic properties. In this Letter, we study the possibility of superconductivity in semiconductor microcavities containing both undoped QWs and thin n-doped semiconductor layers. We show that exciton-polariton mediated superconductivity is possible.Conventional superconductivity occurs at low temperatures and can be described within the framework of BCS theory [10], which relies on the formation of Cooper pairs. Following the discovery of a phonon-mediated attraction between electrons [11], Cooper found that two electrons on top of a Fermi sea always form a bound state, however small the (attractive) interaction between them [12]. This instability results in the so-called BCS state (coherent state of Cooper pairs), that leads to a gap in the spectrum of excitations, responsible for superconductivity. In the currently available high-T C superconductors (the cuprates), an electron pairing is also thought to be realized through a mediating boson, although probably not the phonon [13]. Excitons have been proposed as suitable mediating bosons to achieve higher critical temperatures of superconductivity in specially designed heterostructures ([14], see [15] for a review). As compared to phonons, the characteristic cut-off energy above which the attractive character of the interaction is lost for the excitons is several orders of magnitude higher and the critical temperature is therefore expected to be sufficiently increased with respect to the BCS superconductors. One possible implementation of this idea is the socalled sandw...

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“…The result shows two distinct polariton peaks, with the LP peak asymptotically approaching the exciton energy at larger angles. Signature of a weak middle polariton (MP) branch is also observed, which has been attributed to the effect of charged excitons or trions (X -) [16,18]. The resonances obtained from the electroluminescence spectra are plotted in In order to determine the effect of the polariton-electron scattering in suppressing the bottleneck and enhancing the rate of polariton relaxation to the k || ~ 0 states, we have calculated the polariton occupancy in k-space as a function of n e from the measured angle-resolved electroluminescence data at an injection current density of 4A/cm 2 by using the formula, [19], where η is the collection efficiency, τ C / |C(k || )| 2 is the radiative lifetime of the LPs, M is the number of transverse states included in the detection cone and |C(k || )| 2 is the photon fraction at a wave-vector k || .…”

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confidence: 99%

“…One approach to solving this problem is by introducing polariton-electron scattering, which has been shown both theoretically [15] and experimentally [16][17] to be more efficient than polariton-phonon scattering. Experiments involving polariton-electron scattering typically involve the introduction of a suitable of 2-dimensional electron gas (2DEG) within a wide QW through photo-excitation in an adjacent narrow QW [16][17]. In an electrically injected device with a QW active region, direct doping of the wells would result in broadening of the emission linewidth due to ionized impurity scattering.…”

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confidence: 99%

Polariton emission characteristics of a modulation-doped multiquantum-well microcavity diode

Das

Xiao

Bhowmick

et al. 2012

Applied Physics Letters

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The role of polariton-electron scattering on the performance characteristics of an electrically injected GaAs-based quantum well microcavity diode in the strong coupling regime has been investigated. An electron gas is introduced in the quantum wells by modulation doping with silicon dopants. It is observed that polariton-electron scattering suppresses the relaxation bottleneck in the lower polariton branch. However, it is not adequate to produce a degenerate coherent condensate at k || ~ 0 and coherent emission. *

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Electron-Polariton Scattering in Semiconductor Microcavities

Cited by 60 publications

References 22 publications

Engineering the spatial confinement of exciton polaritons in semiconductors

Engineering the spatial confinement of exciton polaritons in semiconductors

Exciton-Polariton Mediated Superconductivity

Polariton emission characteristics of a modulation-doped multiquantum-well microcavity diode

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