Incoherent excitation and switching of spin states in exciton-polariton condensates

Li, Guangyao; Liew, Timothy Chi Hin; Egorov, Oleg A.; Ostrovskaya, Elena A.

doi:10.1103/physrevb.92.064304

Cited by 21 publications

(29 citation statements)

References 49 publications

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“…With a linearly-polarized pump we have an equal probability of creating a spin-up or spin-down condensate. Although the pump laser is nonresonant with the final polariton states, the initially created carrier spin is not entirely randomized during their multiple carrier-carrier and excitonphonon scatterings [5,28,39,40]. As a result of this incomplete spin relaxation of the excited carriers, changing the ellipticity of the pump breaks the symmetry of the condensate toward the same circular polarization as that of the pump.…”

Section: Spontaneous Buildup Of Circular Polarizationmentioning

confidence: 99%

Spontaneous Spin Bifurcations and Ferromagnetic Phase Transitions in a Spinor Exciton-Polariton Condensate

et al. 2015

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We observe a spontaneous parity breaking bifurcation to a ferromagnetic state in a spatiallytrapped exciton-polariton condensate. At a critical bifurcation density under nonresonant excitation, the whole condensate spontaneously magnetizes and randomly adopts one of two ellipticallypolarized (up to 95% circularly-polarized) states with opposite handedness of polarization. The magnetized condensate remains stable for many seconds at 5 K, but at higher temperatures it can flip from one magnetic orientation to another. We optically address these states and demonstrate the inversion of the magnetic state by resonantly injecting 100-fold weaker pulses of opposite spin. Theoretically, these phenomena can be well described as spontaneous symmetry breaking of the spin degree of freedom induced by different loss rates of the linear polarizations.Condensation of exciton-polaritons (polaritons) spontaneously breaks the global phase symmetry [1][2][3][4][5]. Owing to their easy optical interrogation, high-speed (ps) interactions, and macroscopic coherence (over hundreds of microns) [6], polariton condensates are excellent candidates to probe and exploit for sensing [7,8], spinoptronics [9][10][11], new optoelectronic devices [12][13][14], and quantum simulators [15]. The driven-dissipative multicomponent polariton system can undergo additional bifurcations and condense into states which are not eigenstates of the single-particle Hamiltonian, but many-body states with reduced symmetry [16,17]. Thus, we should expect that two-component exciton-polariton condensates can also show spontaneous symmetry breaking bifurcations in their polarization state. Spin studies of microcavity polaritons have been of great interest in recent years [18][19][20][21][22][23][24][25][26][27][28][29]. However, spontaneous symmetry-breaking bifurcation of spin has not been observed before.Here, we demonstrate spontaneous magnetization in an exciton-polariton condensate, as a direct result of bifurcations in the spin degree of freedom. Utilizing an optically trapped geometry, condensates spontaneously emerge in either of two discrete spin-polarized states that are stable for many seconds, > 10 10 longer than their formation time. These states emit highly circularly-polarized coherent light (up to 95%) and have opposite circular polarizations. The condensate stochastically condenses in a left-or right-circularly polarized state, with an occurrence likelihood that can be controlled by the ellipticity * ho278@cam.ac.uk † jjb12@cam.ac.uk of the nonresonant pump. The two spin-polarized states can be initialized and switched from one state to another with weak resonant optical pulses. Our system has potential applications in sensing, optical spin memories and spin switches, and it can be implemented for studying long-range spin interactions in polariton condensate lattices. This article is structured as follows: in Section I we review trapped polariton condensates and the current understanding of polarization in untrapped polariton condensates. In Section ...

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Section: Spontaneous Buildup Of Circular Polarizationmentioning

confidence: 99%

Spontaneous Spin Bifurcations and Ferromagnetic Phase Transitions in a Spinor Exciton-Polariton Condensate

et al. 2015

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“…Note that in realistic situations, the spin relaxation time of the reservoir is typically finite (see, e.g., Ref. [47]), which can be accounted with a reservoir model in terms of occupations of the left-and right-circular polarized components [41,42] rather than the total density. The dynamics of the polariton condensate can be described by the driven-dissipative two-component Gross-Pitaevskii equation [41,42,45,48], i.e.,…”

Section: Modelmentioning

confidence: 99%

“…We note that our model assumes a spin-independent reservoir resulting from rapid spin relaxation, hence excludes the polarization transfer from the spin-polarized pump to the condensate as discussed in Refs. [41,42] using spin-polarized reservoir models. Moreover, the spontaneous creation of an elliptically polarized condensate in this work is induced by an interplay between interaction effects and linear polarization energy splitting, and occurs for η > 1 which is beyond the typical experimental regime at present.…”

Section: Introductionmentioning

confidence: 99%

Spinor polariton condensates under nonresonant pumping: Steady states and elementary excitations

Zhang

et al. 2017

Phys. Rev. B

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We theoretically investigate a spinor polariton condensate under nonresonant pumping, based on driven-dissipative Gross-Pitaevskii equations coupled to the rate equation of a spin-unpolarized reservoir. We find the homogeneous polariton condensate can transit from the spin-unpolarized phase, where it is linearly polarized, to the spin-polarized phase, where it is elliptically polarized, depending on the cross-spin versus same-spin interactions and the linear polarization splitting. In both phases, we study elementary excitations using Bogoliubov approach, in a regime where the decay rate of total exciton density in reservoir crosses over from the slow to the fast limit. Depending on reservoir parameters, the global-phase mode can be either diffusive or gapped. By contrast, the relative-phase mode always possesses a gapped energy, undamped in the spin-unpolarized phase but weakly damped in the spin-polarized phase. In the spin-unpolarized phase, both modes are linearly polarized despite pumping and decay. However, in the spin-polarized phase, the mode polarization can be significantly affected by the reservoir and depends strongly on the circular polarization degree of the condensate. Interestingly, we demonstrate that the 'ghost' branch of the Bogoliubov spectrum of the relative-phase mode can be visualized in the photoluminescence emission, distinguishable from that of the global-phase mode and thus allowing for experimental observation, when the spinor polariton condensate is elliptically polarized.

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“…[22], we use a nonresonant excitation scheme to ensure that the original coherence of the laser is lost in the relaxation process 25 . We create a polariton condensate with a pseudospin orientation defined by the polarization of the excitation beam 39,40 . As the condensate expands, polaritons propagate over macroscopic distances, whilst their pseudospin collectively precesses.…”

Section: Introductionmentioning

confidence: 99%

Half-skyrmion spin textures in polariton microcavities

et al. 2016

Self Cite

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We study the polarization dynamics of a spatially expanding polariton condensate under nonresonant linearly polarized optical excitation. The spatially and temporally resolved polariton emission reveals the formation of non-trivial spin textures in the form of a quadruplet polarization pattern both in the linear and circular Stokes parameters, and an octuplet in the diagonal Stokes parameter. The continuous rotation of the polariton pseudospin vector through the condensate due to TE-TM splitting exhibits an ordered pattern of half-skyrmions associated with a half-integer topological number. A theoretical model based on a driven-dissipative Gross-Pitaevskii equation coupled with an exciton reservoir describes the dynamics of the nontrivial spin textures through the optical spin-Hall effect.arXiv:1602.04711v2 [physics.optics]

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Incoherent excitation and switching of spin states in exciton-polariton condensates

Cited by 21 publications

References 49 publications

Spontaneous Spin Bifurcations and Ferromagnetic Phase Transitions in a Spinor Exciton-Polariton Condensate

Spontaneous Spin Bifurcations and Ferromagnetic Phase Transitions in a Spinor Exciton-Polariton Condensate

Spinor polariton condensates under nonresonant pumping: Steady states and elementary excitations

Half-skyrmion spin textures in polariton microcavities

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