Anisotropic Superfluid Behavior of a Dipolar Bose-Einstein Condensate

TL;DR

This study demonstrates anisotropic superfluid flow in a dipolar Bose-Einstein condensate of dysprosium, revealing how dipolar interactions cause direction-dependent dissipation and critical velocities, confirmed by experiments and simulations.

Contribution

It provides the first direct transport measurements showing anisotropic superfluid behavior in a dipolar BEC, linking microscopic interactions to macroscopic flow properties.

Findings

Superfluid flow is anisotropic depending on the direction of motion.

Critical velocity for superfluid breakdown varies with direction.

Heating rates above critical velocity reflect anisotropic dissipation.

Abstract

We present transport measurements on a dipolar superfluid using a Bose-Einstein condensate of Dy-162 with strong magnetic dipole-dipole interactions. By moving an attractive laser beam through the condensate we observe an anisotropy in superfluid flow. This observation is compatible with an anisotropic critical velocity for the breakdown of dissipationless flow, which, in the spirit of the Landau criterion, can directly be connected to the anisotropy of the underlying dipolar excitation spectrum. In addition, the heating rate above this critical velocity reflects the same anisotropy. Our observations are in excellent agreement with simulations based on the Gross-Pitaevskii equation and highlight the effect of dipolar interactions on macroscopic transport properties, rendering dissipation anisotropic.