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Item type:Item, Quantum fluctuations and stability of vortex lattices in a nonresonantly pumped exciton-polariton condensate(2017-03-01) ;Chen, Ting-Wei ;Jheng, Shih-Da ;Jiang, T. F. ;Cheng, Szu-Cheng物理研究所The dynamics of an exciton-polariton condensate (EPC) subject to harmonic confinement can cause spontaneously formed vortices to arrange into a triangular vortex lattice. The stability of such a spontaneously formed vortex lattice is still unknown. We investigate the quantum fluctuations of vortex lattices in a rapidly rotating EPC with a rotation frequency close to the harmonic trap. In such a large condensate, we find that a vortex lattice with a triangular structure is stable, whereas one with a square structure becomes unstable. This result indicates that a driven-dissipative vortex array with strong quantum fluctuations can occur in an EPC.Item type:Item, Vortex and trapped states of microcavity-polariton condensates in a harmonic trap(2016-05) ;Chen, Ting-Wei ;Jhen, Shih-Da ;Hsieh, Wen-Feng ;Cheng, Szu-Cheng物理研究所We investigate the vortex and trapped states of a microcavity-polariton condensate in a harmonic trap under non-resonant excitation. The stationary states of the microcavity-polariton condensate are obtained from the complex Gross-Pitaevskii equation numerically. From the excitations of vortices and trapped states, the boundaries separating stable and unstable states are plotted in the phase diagram shown by pump powers versus pump-spot sizes. Our analysis provides physical parameters for experiments of creating stable vortices and trapped states in a trapped microcavity-polariton condensate. (C) 2016 Elsevier B.V. All rights reserved.Item type:Item, Dark solitons in a spinor microcavity-polariton condensate(2016-10) ;Chen, Ting-Wei ;Jheng, Shih-Da ;Hsieh, Wen-Feng ;Cheng, Szu-Cheng物理研究所Dark solitons of a two-component condensate occurring in nonresonantly-pumped microcavity polaritons (spinor MPCs) with integer vorticities, referred to as integer dark solitons (IDSs), can be excited by a laser beam with tunable polarization and power. We investigate the physical properties of stationary IDSs in a pure spinor MPCs without defects. From the excitations of a IDS, we show that the soliton is stable when the pump power is higher than a critical value. When the pump polarization is in favor of one component, we find that the critical pump power for the stabilization becomes higher. The stable IDS exists below a critical pump polarization. A stable phase diagram of IDSs in terms of the pump condition, i.e., pump polarization and power, is thus obtained. (C) 2016 Elsevier Ltd. All rights reserved.Item type:Item, The synchronization and stability of spinor polariton condensates(2016-04) ;Chen, Ting-Wei ;Jheng, Shih-Da ;Hsieh, Wen-Feng ;Cheng, Szu-Cheng物理研究所By taking account of the spin degree of freedom with varying the Zeeman splitting, we explore the possible synchronized states of spinor polariton condensates formed in a semiconductor microcavity. The interplay among nonlinear interactions, spin-flipping rates and energy splitting is theoretically investigated. Besides a minimum transverse field induced spin-flipping rate required to form the synchronized state, we find that the interaction effect between polaritons is the dominant factor. Therefore, with the manipulation of the energy splitting between the two spin states, the spinor condensate initially synchronized with "elliptical" polarization may become two separated desynchronized and "circularly" polarized condensates. Moreover, the region and stability of synchronized states are discussed for various asymmetric pumping configurations. (C) 2016 Elsevier Ltd. All rights reserved.Item type:Item, Drag and critical velocities in a nonresonantly pumped trapped polariton condensate with a rotating defect(2016-01-19) ;Cheng, Szu-Cheng ;Chen, Ting-Wei ;Jheng, Shih-Da ;Hsieh, Wen-Feng物理研究所We model the superfluid properties of a trapped exciton-polariton condensate under non-resonant excitation subjected to a rotating defect. With increasing the linear velocity of rotating defect, the density modulation can be classified into superfluid-like regime, parabolic-like regime, Cherenkov regime and over-Cherenkov regime. The threshold-like behavior of drag force and the onset of turbulent fringes can define the critical velocity for the superfluidity. Based on the perturbative drag force in the Bogoliubov-type analysis, the rigid modes with gapped excitation spectrum have higher critical velocity than that of the soft modes. (C) 2015 Elsevier Ltd. All rights reserved.Item type:Item, Instability of a spontaneously formed multiple-flux vortex in polariton condensates(2015-07-01) ;Chen, Ting-Wei ;Cheng, Szu-Cheng ;Hsieh, Wen-Feng ;光電工程學系Department of PhotonicsA spontaneously formed vortex can occur in an incoherently pumped microcavity-polariton condensate which is a non-equilibrium system. The stability of this vortex depends on the flux quanta that the vortex owns. In this paper, we have investigated the dynamics of spontaneously formed vortices with multiple-flux quanta in incoherently pumped microcavity-polariton condensates. From the excitation spectra of a spontaneously formed vortex, we can study the stability of the vortex under different pump strength. The vortices with flux quanta less than four are dynamically stable within a wide range of pump strength. However, when the flux quanta of a vortex is greater than three and the pump power is above a critical pump strength, some imaginary parts of excitation modes of the vortex become positive. The vortex then becomes dynamically unstable and Lends to split into several vortices with smaller flux quanta. (C) 2015 Elsevier Ltd. All rights reserved.