Direct energy dissipation measurements for a driven superfluid via the harmonic-potential theorem

TL;DR

This paper introduces a novel method to directly measure energy dissipation in a driven superfluid using a perturbed harmonic-potential theorem, validated through experiments on Bose-Einstein condensates and supported by simulations.

Contribution

The paper presents a new experimental technique for quantifying energy dissipation in superfluids via center-of-mass measurements, based on a modified harmonic-potential theorem.

Findings

Observation of superfluid dissipation curves

Identification of a critical velocity dependent on stirrer strength

Agreement between experimental results and mean-field simulations

Abstract

We propose and experimentally demonstrate a method to directly measure energy dissipation for a linearly driven superfluid confined in a harmonic trap. The method relies on a perturbed version of the harmonic-potential theorem, according to which a potential perturbation - effectively acting as a stirrer - converts center-of-mass motional energy into internal energy. Energy conservation then enables a direct, quantitative determination of the dissipated energy from measurements of the macroscopic center-of-mass observables. Applying this method to a perturbed, driven Bose-Einstein condensate, we observe dissipation curves characteristic of superfluid flow, including a critical velocity that depends on the stirrer strength, consistent with previous studies. Our results are supported by mean-field simulations, which corroborate both the theoretical framework and the experimental findings.