# Frustrated Magnetism of Dipolar Molecules on a Square Optical Lattice: Prediction of a Quantum Paramagnetic Ground State

## TL;DR

This paper predicts that dipolar molecules on a square optical lattice can host a quantum paramagnetic ground state, offering a new route to realize quantum spin liquids without complex lattice geometries.

## Contribution

It demonstrates that tilting dipoles in a dipolar Heisenberg model induces frustration leading to a quantum spin liquid phase on a square lattice, which is a novel approach.

## Key findings

- Identification of a quantum paramagnetic region between ordered phases.
- Consistent phase diagrams from multiple theoretical methods.
- Confirmation of a quantum spin liquid state using tensor network techniques.

## Abstract

Motivated by the experimental realization of quantum spin models of polar molecule KRb in optical lattices, we analyze the spin 1/2 dipolar Heisenberg model with competing anisotropic, long-range exchange interactions. We show that, by tilting the orientation of dipoles using an external electric field, the dipolar spin system on square lattice comes close to a maximally frustrated region similar, but not identical, to that of the $J_1$-$J_2$ model. This provides a simple yet powerful route to potentially realize a quantum spin liquid without the need for a triangular or kagome lattice. The ground state phase diagrams obtained from Schwinger-boson and spin-wave theories consistently show a spin disordered region between the N$\acute{\textrm{e}}$el, stripe, and spiral phase. The existence of a finite quantum paramagnetic region is further confirmed by an unbiased variational ansatz based on tensor network states and a tensor renormalization group.