Weak superfluidity in twisted optical potentials

A controlled twist between separate potentials can drastically influence localization properties of quantum particles between ordered and (quasi)disordered limits. Transport properties of single-particle and correlated fermionic materials have been extensively studied in connection with twisted bilayer graphene, but their bosonic counterpart remains largely unexplored. Here, we study bosonic matter in twisted potentials. We use continuous-space quantum Monte Carlo simulations to determine the unique phase diagrams of strongly correlated ultracold bosons in twisted optical lattices. For commensurate twisting angles, spectral gaps govern the formation of insulators, separated by thin superfluid domains. These domains form weak superfluids; with low superfluid fraction at zero temperature and high sensitivity to thermal fluctuations, but may be stabilized under appropriate parameter control. In contrast, slightly changing the twisting angle to an 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 moiré physics.