Slow-Goldstone mode generated by order from quantum disorder and its experimental detection

TL;DR

This paper uncovers a novel phenomenon where order from quantum disorder transforms a quadratic mode into a slow, linear Goldstone mode, with potential for experimental detection in cold atom and photonic systems.

Contribution

It introduces the concept of a slow-Goldstone mode generated by OFQD, supported by a systematic analysis in an interacting bosonic system with Abelian flux, and explores its experimental implications.

Findings

Identification of a slow-Goldstone mode with very small velocity

Demonstration of the phenomenon in weak and strong coupling regimes

Potential observation in cold atom and photonic experiments

Abstract

The order from quantum disorders (OFQD) phenomenon is well-known and ubiquitous in particle physics and frustrated magnetic systems. Typically, OFQD transfers a spurious Goldstone mode into a pseudo-Goldstone mode with a tiny gap. Here, we report an opposite phenomenon: OFQD transfers a spurious quadratic mode into a true linear Goldstone mode with a very small velocity (named slow-Goldstone mode). This new phenomenon is demonstrated in an interacting bosonic system subjected to an Abelian flux. We develop a new and systematic OFQD analysis to determine the true quantum ground state and the whole excitation spectrum. In the weak-coupling limit, the superfluid ground state has a 4-sublattice 90? coplanar spin structure, which supports 4 linear Goldstone modes with 3 different velocities. One of which is generated by the OFQD is much softer than the other 3 Goldstone modes, so it can be easily detected in the cold atom or photonic experiments. In the strong-coupling limit, the ferromagnetic Mott ground state with a true quadratic Goldstone mode. We speculate that there could be some topological phases intervening between the two symmetry broken states. These novel phenomena may be observed in the current cold-atom or photonic experiments subjected to an Abelian flux at the weak coupling limit where the heatings may be well under control. Possible connections to Coleman-Weinberg potential in particle physics, 1/N expansion of Sachdev-Ye-Kitaev models, and zero temperature quantum black hole entropy are outlined.