Synthetic U(1) Gauge Invariance in a Spin-1 Bose Gas

TL;DR

This paper proposes a spin-1 Bose-Einstein condensate setup to simulate the lattice Schwinger model, revealing new gauge-invariant interactions, phase transitions, and quantum scar phenomena in cold-atom quantum simulators.

Contribution

It introduces a novel spin-1 Bose gas model that naturally incorporates U(1) gauge invariance and exhibits new phases and quantum scars not present in traditional models.

Findings

Identification of a new Z3-ordered phase.

Mapping of phase transitions to Ising and Potts universality classes.

Discovery of quantum scars leading to anomalous dynamics.

Abstract

Recent experimental realizations of the lattice Schwinger model [Nature 587, 392 (2020) and Science 367, 1128 (2020)] open a door for quantum simulation of elementary particles and their interactions using ultracold atoms, in which the matter and gauge fields are constrained by a local U(1) gauge invariance known as the Gauss's law. Stimulated by such exciting progress, we propose a new scenario in simulating the lattice Schwinger model in a spin-1 Bose-Einstein condensate. It is shown that our model naturally contains an interaction of the matter fields which respects the U(1) gauge symmetry but has no counterpart in the conventional Schwinger model. In addition to the Z2-ordered phase identified in the previous work, this additional interaction leads to a new Z3-ordered phase. We map out a rich phase diagram and identify that the continuous phase transitions from the disordered to the Z2-ordered and the Z3-ordered phases belong to the Ising and the 3-state Potts universality classes, respectively. Furthermore, the two ordered phases each possess a set of quantum scars which give rise to anomalous quantum dynamics when quenched to a special point in the phase diagram. Our proposal provides a novel platform for extracting emergent physics in cold-atom-based quantum simulators with gauge symmetries.