XY ring-exchange model on the triangular lattice

TL;DR

This paper investigates the XY ring-exchange model on a triangular lattice, revealing a rich phase diagram with gapless excitations, critical correlations, and symmetry-breaking ordered states influenced by different exchange interactions.

Contribution

It introduces a comprehensive analysis of ring-exchange effects on triangular lattices, highlighting the emergence of novel ground states and phase transition behaviors.

Findings

Four-spin exchange results in gapless, critical states.

Nearest-neighbour exchange induces a four-fold ferrimagnetic order.

Finite temperature and magnetic field affect phase transition properties.

Abstract

We study ring-exchange models for bosons or XY-spins on the triangular lattice. A four-spin exchange leads to a manifold of ground states with gapless excitations and critical power-law correlations. With a nearest-neighbour exchange, fluctuations select a four-fold ferrimagnetically ordered ground state with a small spin/superfluid stiffness which breaks the global U(1) and translational symmetry. We explore consequences for phase transitions at finite temperature and in an in-plane magnetic field.