# Steady-state and bistable superradiant phases of an atomic beam traversing an optical cavity

Simon B. Jäger8 , Haonan Liu2 + 2 AuthorsMurray Holland46

Estimated H-index: 8

Estimated H-index: 2

Estimated H-index: 46

Abstract

We investigate the different emission regimes of a pre-excited and collimated atomic beam passing through an optical cavity. In the regime where the cavity degrees of freedom can be adiabatically eliminated, we find that the atoms undergo superradiant emission if the collective linewidth exceeds transit-time broadening. We analyze the case where the atomic beam is not precisely perpendicular to the cavity axis and find a phase of continuous light emission similar to steady-state superradiance for a sufficiently small tilt of the atomic beam. However, if the atoms travel more than half a wavelength along the cavity axis during one transit time we predict a dynamical phase transition to a new bistable superradiant regime. In this phase the atoms undergo collective spontaneous emission with a frequency that is either blue or red detuned of the free-space atomic resonance. We analyze the different superradiant regimes and the quantum critical crossover boundaries. We examine in particular the spectrum of the emitted light and show that the linewidth exhibits features of a critical scaling close to the phase boundaries.