Linear Flavor-Wave Analysis of SU(4)-Symmetric Tetramer Model with Population Imbalance

TL;DR

This paper investigates the phase diagram of an SU(4) symmetric model in a square lattice with population imbalance, revealing a novel intermediate phase with checkerboard order using an extended flavor-wave approach.

Contribution

It introduces an extended linear flavor-wave theory for SU(4) systems with population imbalance and uncovers a new intermediate phase with checkerboard ordering.

Findings

Balanced population leads to local SU(4)-singlet states.

High-field state is a saturated phase with two components.

Identified a checkerboard-like intermediate phase.

Abstract

We study the quantum magnetism of the SU(4) Mott insulator in a square optical superlattice, in which atoms with four nuclear-spin components strongly interact with each other, in the presence of an external field that controls the imbalance between the population of two components and that of the other two. This is a natural extension of the physics of spin-dimer materials under strong magnetic field. We apply an extended linear flavor-wave theory based on four-site plaquettes and unveil the ground-state phase diagram and excitation spectra. When the population of the four components is balanced and the plaquesttes are weakly coupled, the ground state is approximately given by the direct product of local SU(4)-singlet states. In high-field, the system reaches a "saturated state" where only two components are present. Our main finding is a nontrivial intermediate phase, which has a checkerboard-like arrangement of the SU(4)-singlet and four-site resonating-valence-bond states.