Dynamical instability of a driven-dissipative electron-hole condensate in the BCS-BEC crossover region
Ryo Hanai, P. B. Littlewood, Yoji Ohashi
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 to the nonequilibrium 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 antiparallel to $\mathbf{\ensuremath{\nabla}}\ensuremath{\theta}(\mathbit{r})$ [where $\ensuremath{\theta}(\mathbit{r})$ is the phase of the condensate] in the BCS regime, both leading to dynamical instabilities of an exciton BEC. Our results suggest that a substantial region of the exciton-BEC phase in the phase diagram (in terms of the interaction strength and the decay rate) is unstable.
arXiv:1610.08622•Physical review. B./Physical review. B•Sep 28, 2017•28 citations