Quasi-Nambu-Goldstone Modes in Bose-Einstein Condensates

TL;DR

This paper demonstrates that quasi-Nambu-Goldstone modes, previously only theorized in high energy physics, can be realized in Bose-Einstein condensates, revealing new topological defect dynamics and stabilization mechanisms.

Contribution

It introduces the realization of quasi-NG modes in atomic Bose-Einstein condensates and explains their impact on topological defect stability and decay.

Findings

Quasi-NG modes can be realized in Bose-Einstein condensates.

Topological defects become unstable and decay via emission of quasi-NG modes.

Quantum fluctuations stabilize topological defects by giving quasi-NG modes mass.

Abstract

We show that quasi-Nambu-Goldstone (NG) modes, which play prominent roles in high energy physics but have been elusive experimentally, can be realized with atomic Bose-Einstein condensates. The quasi-NG modes emerge when the symmetry of a ground state is larger than that of the Hamiltonian. When they appear, the conventional vacuum manifold should be enlarged. Consequently topological defects that are stable within the conventional vacuum manifold become unstable and decay by emitting the quasi-NG modes. Contrary to conventional wisdom, however, we show that the topological defects are stabilized by quantum fluctuations that make the quasi-NG modes massive, thereby suppressing their emission.