Geometric and fluctuational divergences in the linear response of coherently driven microcavity polaritons and their relation to superfluidity

This is the authors' abstract. We don't add key points for this paper.

We consider the possibility of superfluid behavior in a coherently driven, dissipative microcavity polariton system in gapless spectrum regimes. Previous work demonstrated the absence of such behavior for gapped spectra via a linear response analysis. The system can, however, be tuned to possess a gapless spectrum in special cases, leaving open the possibility of superfluid behavior. Here we show the absence of superfluidity in all regimes; we find a divergent linear response in the system's gapless regimes, which may be linked to phase-transition behavior. This indicates that the gapless spectrum is related to phase instability and not superfluid-enabling massless modes.