Tunable Superfluidity and Quantum Magnetism with Ultracold Polar Molecules

TL;DR

This paper introduces a highly tunable model for ultracold polar molecules in optical lattices, enabling exploration of superfluidity and quantum magnetism through adjustable long-range dipolar interactions.

Contribution

It presents the t-J-V-W model with independent control over all interaction parameters, extending the traditional t-J model to include density and density-spin interactions.

Findings

DMRG used to map the 1D phase diagram of the model

Long-range interactions enhance superfluidity

Bloch oscillations can probe the phase diagram experimentally

Abstract

By selecting two dressed rotational states of ultracold polar molecules in an optical lattice, we obtain a highly tunable generalization of the t-J model, which we refer to as the t-J-V-W model. In addition to XXZ spin exchange, the model features density-density interactions and novel density-spin interactions; all interactions are dipolar. We show that full control of all interaction parameters in both magnitude and sign can be achieved independently of each other and of the tunneling. As a first step towards demonstrating the potential of the system, we apply the density matrix renormalization group method (DMRG) to obtain the 1D phase diagram of the simplest experimentally realizable case. Specifically, we show that the tunability and the long-range nature of the interactions in the t-J-V-W model enable enhanced superfluidity. Finally, we show that Bloch oscillations in a tilted lattice can be used to probe the phase diagram experimentally.