Superfluidity of Bose-Einstein condensates in toroidal traps with nonlinear lattices

TL;DR

This paper explores the superfluid behavior of Bose-Einstein condensates in toroidal traps with nonlinear lattices, demonstrating stable wave formations, persistent currents, and the effects of defects on superfluidity.

Contribution

It introduces the existence of various stable periodic waves in BECs with nonlinear lattices and analyzes their superfluid properties and response to defects.

Findings

Stable periodic wave solutions exist in BECs with nonlinear lattices.

Persistent atomic currents and Bogoliubov spectra are supported by these waves.

Linear defects do not disrupt superfluidity at subcritical velocities.

Abstract

Superfluid properties of Bose-Einstein condensates (BEC) in toroidal quasi-one-dimensional traps are investigated in the presence of periodic scattering length modulations along the ring. The existence of several types of stable periodic waves, ranging from almost uniform to very fragmented chains of weakly interacting and equally spaced solitons, is demonstrated. We show that these waves may support persistent atomic currents and sound waves with spectra of Bogoliubov type. Fragmented condensates can be viewed as arrays of Josephson junctions and the current as a BEC manifestation of the dc-Josephson effect. The influence of linear defects on BEC superfluidity has been also investigated. We found that for subcritical velocities, linear defects that are static with respect to the lattice (while the condensate moves in respect to both the optical lattice and the defect) preserve the BEC superfluidity.