Spontaneous symmetry breaking and collapse in bosonic Josephson junctions

TL;DR

This paper numerically maps the phase diagram of an attractive Bose-Einstein condensate in a double-well trap, revealing Josephson, symmetry-breaking, and collapse phases, and explores their dynamics for ultracold lithium atoms.

Contribution

First numerical quantum phase diagram including Josephson, SSB, and collapse phases for attractive BECs in a double-well trap.

Findings

Identified all three key phases in the system.

Calculated population-imbalance mode frequencies.

Proposed experimental observation with ultracold 7Li vapors.

Abstract

We investigate an attractive atomic Bose-Einstein condensate (BEC) trapped by a double-well potential in the axial direction and by a harmonic potential in the transverse directions. We obtain numerically, for the first time, a quantum phase diagram which includes all the three relevant phases of the system: Josephson, spontaneous symmetry breaking (SSB), and collapse. We consider also the coherent dynamics of the BEC and calculate the frequency of population-imbalance mode in the Josephson phase and in the SSB phase up to the collapse. We show that these phases can be observed by using ultracold vapors of 7Li atoms in a magneto-optical trap.