Dynamical instability of a driven-dissipative electron-hole condensate in the BCS-BEC-crossover region

Ryo Hanai; Peter B. Littlewood; Yoji Ohashi

doi:10.1103/physrevb.96.125206

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arXiv · 1610.08622

Dynamical instability of a driven-dissipative electron-hole condensate in the BCS-BEC-crossover region

Ryo Hanai·Peter B. Littlewood·Yoji Ohashi

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Abstract

We present a stability analysis on a driven-dissipative electron-hole condensate in the BCS (Bardeen-Cooper-Schrieffer)-BEC (Bose-Einstein-condensation)-crossover region. Extending the combined BCS-Leggett theory with the generalized random phase approximation (GRPA) to the non-equilibrium case by employing the Keldysh formalism, we show that the pumping-and-decay of carriers causes a depairing effect on excitons. This phenomenon gives rise to an attractive interaction between excitons in the BEC regime, as well as a supercurrent that anomalously flows anti-parallel to $\nabla θ({\bf r})$ (where $θ({\bf r})$ is the phase of the condensate) in the BCS regime, both leading to dynamical instabilities of an exciton-BEC. Our result suggests that substantial region of the exciton-BEC phase in the phase diagram (in terms of the interaction strength and the decay rate) is unstable.

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Ryo Hanai, Peter B. Littlewood, Yoji Ohashi. 2017-09-04. Dynamical instability of a driven-dissipative electron-hole condensate in the BCS-BEC-crossover region. https://doi.org/10.1103/physrevb.96.125206

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