Superfluidity breakdown of periodic matter waves in quasi one-dimensional annular traps via resonant scattering with moving defects

TL;DR

This paper explores how resonant scattering with moving defects causes superfluidity breakdown in periodic Bose-Einstein condensates in quasi-1D ring traps, revealing conditions for maintaining or restoring superfluidity.

Contribution

It provides a detailed analytical and numerical study of superfluidity breakdown mechanisms in BECs with optical lattices and moving defects, highlighting the role of resonant scattering and ring size.

Findings

Moving defects cause superfluidity breakdown regardless of velocity.

Weak optical lattices allow long-time quasi-superfluidity.

Small ring sizes can prevent resonant scattering and restore superfluidity.

Abstract

We investigate, both analytically and numerically, the quasi-superfluidity properties of periodic Bose-Einstein condensates (BECs) in a quasi-one-dimensional (1D) ring with optical lattices (OL) of different kinds (linear and nonlinear) and with a moving defect of an infinite mass inside. To study the dynamics of the condensate we used a mean-field approximation describing the condensate by use of the Gross-Pitaevskii equation for the order parameter. We show that the resonant scattering of sound Bloch waves with the defect profoundly affect BEC superfluidity. In particular, a moving defect always leads to the breakdown of superfluidity independently of the value of its velocity. For weak periodic potentials the superfluidity breakdown may occur on a very long time scale (quasisuperfluidity) but the breakdown process can be accelerated by increasing the strength of the OL. Quite remarkably, we find that when the length of the ring is small enough to imply the discreteness of the reciprocal space, it becomes possible to avoid the resonant scattering and to restore quasi-superfluidity.