Build up and pinning of linear polarization in the Bose condensates of exciton polaritons

Kasprzak, Jacek; André, R.; Dang, Le Si; Shelykh, I. A.; Kavokin, Alexey; Rubo, Yuri G.; Kavokin, K. V.; Malpuech, Guillaume

doi:10.1103/physrevb.75.045326

Cited by 98 publications

(79 citation statements)

References 19 publications

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“…The linear polarization vector of the condensate has the same direction at each point in the real space. Our sample is disordered, which is why the polarization vector of the condensate is always pinned to one of the crystal axes [28,29]. For higher pumping levels, we observe a depinning of the polarization vector, which is manifested in a decrease of the total DOLP with respect to the pump power [30].…”

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confidence: 79%

Ghost Branch Photoluminescence From a Polariton Fluid Under Nonresonant Excitation

et al. 2015

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An expanding polariton condensate is investigated under pulsed nonresonant excitation with a small laser pump spot. Far above the condensation threshold we observe a pronounced increase in the dispersion curvature, with a subsequent linearization of the spectrum and strong luminescence from a ghost branch orthogonally polarized with respect to the linearly polarized condensate emission. Polarization of both branches is understood in terms of spin-dependent polariton-polariton scattering. The presence of the ghost branch has been confirmed in time-resolved measurements. The effects of disorder and dissipation in the photoluminescence of polariton condensates and their excitations are discussed. DOI: 10.1103/PhysRevLett.115.186401 PACS numbers: 71.36.+c, 67.10.-j, 71.35.Lk, 78.67.De Exciton polaritons are composite bosons consisting of strongly coupled microcavity photons and quantumwell excitons. They are able to form a novel class of condensates (for recent reviews see, e.g., [1,2]). Despite their nonequilibrium and dissipative nature, they behave as condensates of weakly interacting bosons. Collective phenomena like condensation [3], off-diagonal long-range order [4,5], topological excitations [6], or superfluid features in the propagation of polariton flows [7] have been demonstrated in such systems. A spectacular consequence of the parametric scattering in polariton gases is the appearance of nonparabolic scattering bands, including normal branches (NBs) and ghost branches (GBs), where the latter are populated by the virtual off-branch excitonpolaritons [7,8]. Excitations of polariton condensates are expected to be characterized by linearized dispersions of the Bogoliubov-like spectra [9]. The fluid excitations at low momenta are expected to behave as collective sound waves rather than as single particles. Recently, the linear dispersion NB and the GB of a resonantly pumped polariton condensate [10] have been observed in a four-wave mixing experiment.The experiment providing direct access to the dispersion of excitations of spontaneously formed condensates in polariton systems is photoluminescence (PL) under nonresonant excitation. The nonresonant pumping can be realized with either a detuned laser or the current injection [11,12]. In the nonresonant pumping scheme, incoherent excitons are generated and then relax, subsequently feeding the reservoir and governing the dynamics of the system [13]. The relaxation of the created hot excitons involves multiple-scattering processes, which destroy the coherence and phase of the excitation; this ensures that these properties are not inherited by the condensate, in contrast to the resonant excitation case. At the same time, the incoherent reservoir causes additional decoherence [14], forming a repulsive potential [15] which shapes the condensate spatially and spectrally. Moreover, it significantly affects the excitation spectrum of the condensate [16]. Bogoliubov dispersions have been reported in this excitation scheme; however, no fingerprints of the GB have been...

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confidence: 79%

Ghost Branch Photoluminescence From a Polariton Fluid Under Nonresonant Excitation

et al. 2015

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“…there is an attractive interaction between opposite spin species, 1,28 due to asymmetry at the quantum-well interfaces, 23 or may be induced by electric fields 24 or stress. 25 Put together, these yield the coupled cGPE,…”

Section: Model For Spinor Polaritonsmentioning

confidence: 99%

“…25 Such terms will again induce interactions between vortices of the left-and right-circular polarization, and if strong enough, will lead to a pinning of the polarization of a polariton condensate, as has been observed in experiment. 1,[26][27][28] Considering the splitting of linear polarizations as a phase-locking term between the two circular polarization components, and combining this with a magnetic field that favors one or other circular polarization, one has a Josephson problem, 29 where the energy favoring linear polarization is a Josephson coupling, and the magnetic field leads to a bias between the two fields. Shelykh et al 30 have considered the interplay between these spinor Josephson oscillations, and Josephson coupling between two different spatial modes of a trapped polariton condensate, showing that complex behavior can arise in this four-mode system without pumping and decay.…”

Section: Introductionmentioning

confidence: 99%

Spatial pattern formation and polarization dynamics of a nonequilibrium spinor polariton condensate

2010

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Quasiparticles in semiconductors-such as microcavity polaritons-can form condensates in which the steady-state density profile is set by the balance of pumping and decay. By taking account of the polarization degree of freedom for a polariton condensate, and considering the effects of an applied magnetic field, we theoretically discuss the interplay between polarization dynamics, and the spatial structure of the pumped decaying condensate. If spatial structure is neglected, this dynamics has attractors that are linearly polarized condensates ͑fixed points͒, and desynchronized solutions ͑limit cycles͒, with a range of bistability. Considering spatial fluctuations about the fixed point, the collective spin modes can either be diffusive, linearly dispersing, or gapped. Including spatial structure, interactions between the spin components can influence the dynamics of vortices; produce stable complexes of vortices and rarefaction pulses with both co-and counter-rotating polarizations; and increase the range of possible limit cycles for the polarization dynamics, with different attractors displaying different spatial structures.

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“…This is why the HQV and integer phase vortices may coexist within the same condensate. The underlying mechanisms for the polarization splitting are thought to be the different penetration depths in the distributed Bragg reflectors (microcavity mirrors) for transverse electric and transverse magnetic polarizations (22) and the intrinsic anisotropy of the microcavity (23,24). The anisotropy is expected to be the product of a number of parameters, including the alloy concentrations, the wedge, quantum well width fluctuations, and the built-in strain.…”

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confidence: 99%

Observation of Half-Quantum Vortices in an Exciton-Polariton Condensate

Lagoudakis

Ostatnický

Kavokin

et al. 2009

Science

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334

302

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Singly quantized vortices have already been observed in many systems, including the superfluid helium, Bose-Einstein condensates of dilute atomic gases, and condensates of exciton-polaritons in the solid state. Two-dimensional superfluids carrying spin are expected to demonstrate a different type of elementary excitations referred to as half-quantum vortices, characterized by a p rotation of the phase and a p rotation of the polarization vector when circumventing the vortex core. We detect half-quantum vortices in an exciton-polariton condensate by means of polarization-resolved interferometry, real-space spectroscopy, and phase imaging. Half-quantum vortices coexist with single-quantum vortices in our sample.

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Build up and pinning of linear polarization in the Bose condensates of exciton polaritons

Abstract: 5 pagesInternational audienc

Cited by 98 publications

References 19 publications

Ghost Branch Photoluminescence From a Polariton Fluid Under Nonresonant Excitation

Ghost Branch Photoluminescence From a Polariton Fluid Under Nonresonant Excitation

Spatial pattern formation and polarization dynamics of a nonequilibrium spinor polariton condensate

Observation of Half-Quantum Vortices in an Exciton-Polariton Condensate

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