Nonequilibrium polariton condensation in biannular optically induced traps

We report the mean field model of nonequilibrium polariton condensation in annular effective non-Hermitian potential traps, stemming from incoherent optically induced excitonic reservoirs of annular shape. We solve the linearized extended Gross-Pitaevskii equation in the approximation of two delta-function effective shell potentials for complex spectra of trapped polariton modes and calculate corresponding condensation threshold optical pumping powers. The exhaustive map of condensate quantum number transitions in the multi-dimensional space of trap parameters, including a cascade of topological charge increments, is drastically different from the single annular trap case in topology and the range of accessible condensate states.Comment: 9 pages, 6 figure

Ratchet effects in two-dimensional systems with a lateral periodic potential

Radiation-induced ratchet electric currents have been studied theoretically in graphene with a periodic noncentrosymmetric lateral potential. The ratchet current generated under normal incidence is shown to consist of two contributions, one of them being polarization-independent and proportional to the energy relaxation time, and another controlled solely by elastic scattering processes and sensitive to both the linear and circular polarization of radiation. Two realistic mechanisms of electron scattering in graphene are considered. For short-range defects, the ratchet current is helicity-dependent but independent of the direction of linear polarization. For the Coulomb impurity scattering, the ratchet current is forbidden for the radiation linearly polarized in the plane perpendicular to the lateral-potential modulation direction. For comparison, the ratchet currents in a quantum well with a lateral superlattice are calculated at low temperatures with allowance for the dependence of the momentum relaxation time on the electron energy.Comment: 8 pages, 4 figure

Spontaneous polariton currents in periodic lateral chains

We predict spontaneous generation of superfluid polariton currents in planar microcavities with lateral periodic modulation of both potential and decay rate. A spontaneous breaking of spatial inversion symmetry of a polariton condensate emerges at a critical pumping, and the current direction is stochastically chosen. We analyse the stability of the current with respect to the fluctuations of the condensate. A peculiar spatial current domain structure emerges, where the current direction is switched at the domain walls, and the characteristic domain size and lifetime scale with the pumping power.Comment: 6+6 pages, 4+1 figures (with supplemental material