Temperatures are not useful to characterise bright-soliton experiments for ultra-cold atoms

Abstract

Contrary to many other translationally invariant one-dimensional models, the low-temperature phase for an attractively interacting one-dimensional Bose-gas (a quantum bright soliton) is stable against thermal fluctuations. However, treating the thermal properties of quantum bright solitons within the canonical ensemble leads to anomalous fluctuations of the total energy that indicate that canonical and micro-canonical ensembles are not equivalent. State-of-the-art experiments are best described by the micro-canonical ensemble, within which we predict a co-existence between single atoms and solitons even in the thermodynamic limit - contrary to strong predictions based on both the Landau hypothesis and the canonical ensemble. This questions the use of temperatures to describe state-of-the-art bright soliton experiments that currently load Bose-Einstein condensates into quasi-one-dimensional wave guides without adding contact to a heat bath.

6 pages, 1 figure (preprint version)

References in corpus (5)

• Formation of bright matter-wave solitons during the collapse of Bose-Einstein condensates
• Collisions of matter-wave solitons
• Fluctuations of composite observables and stability of statistical systems
• Death of soliton trains in attractive Bose-Einstein condensates
• Condensation of N interacting bosons: Hybrid approach to condensate fluctuations