Weak Superfluidity in Twisted Optical Potentials

TL;DR

This paper uses quantum Monte Carlo simulations to explore phase diagrams of ultracold bosons in twisted optical potentials, revealing weak superfluid phases and Bose glass states influenced by twisting angles and thermal effects.

Contribution

It provides the first detailed phase diagrams of strongly-correlated bosons in twisted optical lattices, highlighting the effects of commensurate and incommensurate twists on quantum phases.

Findings

Weak superfluids form at commensurate angles and are sensitive to temperature.

Spectral gaps lead to insulating patterns separated by superfluid regions.

Incommensurate twists destroy spectral gaps, resulting in Bose glass phases.

Abstract

A controlled twist between different underlying lattices allows one to interpolate, under a unified framework, across ordered and (quasi-)disordered matter while drastically changing quantum transport properties. Here, we use quantum Monte Carlo simulations to determine the unique phase diagrams of strongly-correlated ultracold bosons in twisted optical potentials. We show that at commensurate twisting angles, spectral gaps govern the formation of insulating patterns, separated by thin superfluid domains. The latter form weak superfluids, which are very sensitive to thermal fluctuations, but can be stabilized under appropriate parameter control. In contrast, slightly changing the twisting angle to a incommensurate value destroys most spectral gaps, leaving behind a prominent Bose glass phase. Our results are directly applicable to current generation experiments that quantum simulate moir\'e physics.