Mott-insulating phases of the Bose-Hubbard model on quasi-1D ladder lattices

TL;DR

This paper investigates the phase diagram of the Bose-Hubbard model on quasi-1D ladder lattices, revealing the persistence of the rung-Mott insulator phase at finite interactions and how lattice connectivity influences phase boundaries.

Contribution

It provides the first detailed calculation of the RMI phase boundary in a ladder lattice considering finite on-site interactions and explores how lattice structure affects phase stability.

Findings

RMI phase persists at finite interactions

Phase boundaries are calculated in the thermodynamic limit

Number and parity variances can distinguish phases

Abstract

We calculate the phase diagram of the Bose-Hubbard model on a half-filled ladder lattice including the effect of finite on-site interactions. This shows that the rung-Mott insulator (RMI) phase persists to finite interaction strength, and we calculate the RMI-superfluid phase boundary in the thermodynamic limit. We show that the phases can still be distinguished using the number and parity variances, which are observables accessible in a quantum-gas microscope. Phases analogous to the RMI were found to exist in other quasi-1D lattice structures, with the lattice connectivity modifying the phase boundaries. This shows that the the presence of these phases is the result of states with one-dimensional structures being mapped onto higher dimensional systems, driven by the reduction of hopping rates along different directions.