Temperature induced decay of persistent currents in a superfluid ultracold gas

TL;DR

This study investigates how increasing temperature reduces the lifetime of persistent currents in a superfluid Bose-Einstein condensate, revealing the importance of thermal fluctuations in critical velocity behavior.

Contribution

It provides experimental insights into temperature effects on superfluid persistent currents and challenges existing models by showing their inadequacy in explaining decay rates.

Findings

Persistent current lifetime decreases with temperature.

Critical velocity depends strongly on temperature.

Simple thermal activation and tunneling models do not match observed decay rates.

Abstract

We study how temperature affects the lifetime of a quantized, persistent current state in a toroidal Bose-Einstein condensate (BEC). When the temperature is increased, we find a decrease in the persistent current lifetime. Comparing our measured decay rates to simple models of thermal activation and quantum tunneling, we do not find agreement. We also measured the size of hysteresis loops size in our superfluid ring as a function of temperature, enabling us to extract the critical velocity. The measured critical velocity is found to depend strongly on temperature, approaching the zero temperature mean-field solution as the temperature is decreased. This indicates that an appropriate definition of critical velocity must incorporate the role of thermal fluctuations, something not explicitly contained in traditional theories.