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

Abstract

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.

Persistent current by a static non-Hermitian ratchet

“…Quantum interferometers [4] and "polariton circuits" [66][67][68][69] can be implemented in this 2D platform. In addition, degrees of freedom the exciton-spin can be taken into consideration [70][71][72][73][74][75][76]. The transport of spinor exciton-polariton condensates [71,77,78] might also be an interesting problem with rich applications.…”

Nonequilibrium Landau-Zener tunneling in exciton-polariton condensates

“…It is a nonequilibrium system because the lifetime of polaritons is short and needs to be replenished by a pump laser. There are lots of work discuss the steady states and elementary excitations of polari- * The corresponding author: zhxliang@gmail.com tons in both one and two components condensates theoretically and experimentally [9][10][11][12][13][14][15][16][17][18][19], meanwhile, nonlinear phenomena like oblique dark solitons, vortices, bright solitons and dark-bright solitons in dissipative system bring a new research field [20][21][22][23][24][25][26][27][28]. Spontaneous oscillations in a microcavity polariton bosonic Josephson junction with strong imbalance of the population have been observed in a double-well [29][30][31][32] which arise more interests in studying polaritons in periodic potential.…”

Drag force of a exciton-polariton condensate under non-resonant pumping

“…Similar to the ultracold atomic BEC, the typical aspects of superfluid behavior of a polariton condensate such as quantized vortices [7][8][9], suppression of scattering off disorder [10,11], and the Bogoliubov's excitations [12,13] have been observed experimentally. On the other hand, going beyond the equilibrium superfluid, the intrinsically non-equilibrium nature of a polariton condensate captured by the dissipation has induced the Goldstone mode [14][15][16][17] of a spatially homogeneous system to be diffusive and made ghost branches [18] of Bogoliubov excitations to be observable. These remarkable properties of the non-equilibrium superfluid prompt questions about superfluidity definition of superfluidity and characteristic observables [19][20][21][22][23].…”