Parity Symmetry Breaking and Topological Phases in a Superfluid Ring

TL;DR

This paper analytically investigates phase transitions and topological phenomena in a superfluid Bose-Einstein condensate confined in a ring with a rotating barrier, revealing symmetry breaking and hysteresis effects.

Contribution

It introduces a detailed analytical model of parity symmetry breaking and topological phase transitions in a superfluid ring with a rotating barrier, connecting theory with experimental observations.

Findings

Identification of a parity symmetry-breaking phase transition at a critical barrier height.

Observation of a discontinuous, hysteresis-associated phase transition when changing barrier velocity.

Analysis of the current-phase relation and its agreement with experimental data.

Abstract

We study analytically the superfluid flow of a Bose-Einstein condensate in a ring geometry in presence of a rotating barrier. We show that a phase transition breaking a parity symmetry among two topological phases occurs at a critical value of the height of the barrier. Furthermore, a discontinuous (accompanied by hysteresis) phase transition is observed in the ordered phase when changing the angular velocity of the barrier. At the critical point where the hysteresis area vanishes, chemical potential of the ground state develops a cusp (a discontinuity in the first derivative). Along this path, the jump between the two corresponding states having a different winding number shows strict analogies with a topological phase transition. We finally study the current-phase relation of the system and compare some of our calculations with published experimental results.