Supersolid properties of a Bose-Einstein condensate in a ring resonator

TL;DR

This paper explores the coexistence of superfluidity and crystalline order in a Bose-Einstein condensate within a ring resonator, revealing a supersolid phase characterized by spontaneous symmetry breaking and phase coherence.

Contribution

It demonstrates the experimental realization and theoretical analysis of a supersolid phase in a BEC coupled to a ring resonator, highlighting the conditions for its emergence and stability.

Findings

Identification of superfluid, supersolid, and dynamic phases.

Observation of a steady state with crystalline order breaking translational symmetry.

Demonstration of phase coherence across the superfluid to supersolid transition.

Abstract

We investigate the dynamics of a Bose-Einstein condensate interacting with two non-interfering and counterpropagating modes of a ring resonator. Superfluid, supersolid and dynamic phases are identified experimentally and theoretically. The supersolid phase is obtained for sufficiently equal pump strengths for the two modes. In this regime we observe the emergence of a steady state with crystalline order, which spontaneously breaks the continuous translational symmetry of the system. The supersolidity of this state is demonstrated by the conservation of global phase coherence at the superfluid to supersolid phase transition. Above a critical pump asymmetry the system evolves into a dynamic run-away instability commonly known as collective atomic recoil lasing. We present a phase diagram and characterize the individual phases by comparing theoretical predictions with experimental observations.