Two-Dimensional Quantum XY Model with Ring Exchange and External Field

TL;DR

This paper maps the zero-temperature phase diagram of a 2D quantum XY model with ring exchange and external field, revealing multiple quantum phase transitions but no spin liquid phase.

Contribution

It provides the first comprehensive quantum Monte Carlo analysis of the phase diagram for this specific model with ring exchange and external magnetic field.

Findings

Identified phase transitions between XY-order, striped, valence bond solid, and Neel antiferromagnetic states.

Found no evidence of a quantum spin liquid phase.

Mapped the complete zero-temperature phase diagram.

Abstract

We present the zero-temperature phase diagram of a square lattice quantum spin 1/2 XY model with four-site ring exchange in a uniform external magnetic field. Using quantum Monte Carlo techniques, we identify various quantum phase transitions between the XY-order, striped or valence bond solid, staggered Neel antiferromagnet and fully polarized ground states of the model. We find no evidence for a quantum spin liquid phase.