Topological superfluid transition in bubble-trapped condensates

TL;DR

This paper studies the topological superfluid transition in bubble-trapped condensates, revealing universal scaling laws and proposing experimental observation methods for finite-temperature hydrodynamic excitations.

Contribution

It extends the BKT theory to finite spherical systems and uncovers universal scaling relations for the superfluid transition in bubble-trapped condensates.

Findings

Universal scaling relations for critical temperature.

Finite width of the superfluid transition.

Experimental observability via hydrodynamic excitations.

Abstract

Ultracold quantum gases are highly controllable and, thus, capable of simulating difficult quantum many-body problems ranging from condensed matter physics to astrophysics. Although experimental realizations have so far been restricted to flat geometries, recently also curved quantum systems, with the prospect of exploring tunable geometries, are produced in microgravity facilities as ground-based experiments are technically limited. Here we analyze bubble-trapped condensates, in which the atoms are confined on the surface of a thin spherically-symmetric shell by means of external magnetic fields. A thermally-induced proliferation of vorticity yields a vanishing of superfluidity. We describe the occurrence of this topological transition by conceptually extending the theory of Berezinskii, Kosterlitz and Thouless for infinite uniform systems to such finite-size systems. Unexpectedly, we find universal scaling relations for the mean critical temperature and the finite width of the superfluid transition. Furthermore, we elucidate how they could be experimentally observed in finite-temperature hydrodynamic excitations.