Symmetry breaking, Josephson oscillation and self-trapping in a self-bound three-dimensional quantum ball

TL;DR

This paper investigates symmetry breaking, Josephson oscillation, and self-trapping phenomena in a three-dimensional quantum ball stabilized by specific interactions, revealing dynamic behaviors under various potential configurations.

Contribution

It introduces a detailed analysis of SSB, Josephson oscillation, and self-trapping in a 3D quantum ball with novel potential setups, combining variational and numerical methods.

Findings

SSB leads to doubly-degenerate ground states.

Small displacements cause oscillations with self-trapping.

Medium displacements result in asymmetric Josephson oscillations.

Abstract

We study spontaneous symmetry breaking (SSB), Josephson oscillation, and self-trapping in a stable, mobile, three-dimensional matter-wave spherical quantum ball self-bound by attractive two-body and repulsive three-body interactions. The SSB is realized by a parity-symmetric (a) one-dimensional (1D) double-well potential and (b) a 1D Gaussian potential, both along the $z$ axis and no potential along the $x$ and $y$ axes. In the presence of each of these potentials, the symmetric ground state dynamically evolves into a doubly-degenerate SSB ground state. If the SSB ground state in the double well, predominantly located in the first well ($z>0$), is given a small displacement, the quantum ball oscillates with a self-trapping in the first well. For a medium displacement one encounters an asymmetric Josephson oscillation. The asymmetric oscillation is a consequence of SSB. The study is performed by a variational and numerical solution of a non-linear mean-field model with 1D parity-symmetric perturbations.