Self-Trapping, Quantum Tunneling and Decay Rates for a Bose Gas with Attractive Nonlocal Interaction

TL;DR

This paper investigates the behavior of a Bose-Einstein condensate of lithium-7 atoms with attractive nonlocal interactions, revealing new stable states, analyzing quantum tunneling between states, and calculating decay rates due to inelastic collisions.

Contribution

It introduces a new stable high-density branch in the condensate and analyzes quantum tunneling and decay rates in this system.

Findings

Discovery of a new high-density stable branch.

Macroscopic quantum self-trapped configuration at high densities.

Quantitative analysis of tunneling and decay rates.

Abstract

We study the Bose-Einstein condensation for a cloud of $^7$Li atoms with attractive nonlocal (finite-range) interaction in a harmonic trap. In addition to the low-density metastable branch, that is present also in the case of local interaction, a new stable branch appears at higher densities. For a large number of atoms, the size of the cloud in the stable high-density branch is independent of the trap size and the atoms are in a macroscopic quantum self-trapped configuration. We analyze the macroscopic quantum tunneling between the low-density metastable branch and the high-density one by using the istanton technique. Moreover we consider the decay rate of the Bose condensate due to inelastic two- and three-body collisions.