Stable Dark Soliton(train)in Polariton Condensate

A new excited state is generated under the strong coupling of the semiconductor exciton and the microcavity photon,which is called polariton.The effective mass of polaritons is very small,about 10^-4-10^-55 times of the electron mass,which makes it possible to achieve polariton Bose-Einstein condensation at several Kelvin or even room temperature.The realization of polariton BEC not only makes non-low temperature solid-state Bose-Einstein condensation a hot topic,but also expands the development and application of quantum devices in the future.In this paper,we mainly talk about the existence and stability of dark soliton in polariton condensate,and control the quantity of stable dark solitons.The research progress of polariton is introduced firstly.Secondly,the structure of semiconductor microcavity is presented.The basic theory of exciton and polariton are described,and then the Gross-Pitaevskii equation is deduced.Finally,with the use of an appropriate defect potential and homogeneous pumping,we demonstrate the existence of stable dark/anti-dark solitons in spatially separated exciton-polariton condensate.The solitons are not spontaneously created during the polariton condensate formation,but after a sudden phase transition from a pair of unstable dark solitons.Although a method has been proposed to stabilize the dark soliton by use of both coherent pulse and nonresonant periodic pump fields,we note that our solution is qualitatively different from the solitons found in previous works:the key ingredient is the phase coupling of the polariton dyad,and the phase configuration tends to pick the state with the highest number of particles.Within this scheme,the dissipative solitons in nonequilibrium polariton condensate appear to be similar to the ones present in Hamiltonian systems:they may be stable.On the basis of obtaining a stable dark soliton,we continue to explore the existence of several stable dark solitons,by regulating the width of potential defect and the value of potential to change the number of dark solitons.At the same time we try to prove the stability of the dark soliton train.