Bosonic Mott Insulator with Meissner Currents

TL;DR

This paper presents a bosonic lattice model demonstrating that Meissner currents, typically associated with superconductivity, can exist in insulating phases through a spin superfluid, with potential realizations in cold atoms and Josephson arrays.

Contribution

It introduces a new bosonic model showing spin Meissner effects in Mott insulators, highlighting long-range spin coherence in insulating phases.

Findings

Charge sector is gapped in Mott insulator phase.

Spin sector remains superfluid with Meissner currents.

Phase diagram includes chiral currents and spin-density wave phases.

Abstract

We introduce a generic bosonic model exemplifying that (spin) Meissner currents can persist in insulating phases of matter. We consider two species of interacting bosons on a lattice. Our model exhibits separation of charge (total density) and spin (relative density): The charge sector is gapped in a bosonic Mott insulator phase with total density one, while the spin sector remains superfluid due to interspecies conversion. Coupling the spin sector to the gauge fields yields a spin Meissner effect reflecting the long-range spin superfluid coherence. We investigate the resulting phase diagram and describe other possible spin phases of matter in the Mott regime possessing chiral currents as well as a spin-density wave phase. The model presented here is realizable in Josephson junction arrays and in cold atom experiments.