Competing valence bond and symmetry breaking Mott states of spin-3/2 fermions on a honeycomb lattice

TL;DR

This paper explores the magnetic phases of spin-3/2 fermions on a honeycomb lattice, revealing a competition between symmetry-breaking and disordered valence bond states, including an SU(4) symmetric phase.

Contribution

It introduces a mean-field phase diagram for spin-3/2 fermions, identifying novel valence bond states and the conditions for their emergence.

Findings

Identification of valence bond states with bond-centered magnetizations

Discovery of an SU(4) symmetric valence bond phase

Phase diagram showing competition between magnetic orders

Abstract

We investigate magnetic properties of strongly interacting four component spin-3/2 ultracold fermionic atoms in the Mott insulator limit with one particle per site in an optical lattice with honeycomb symmetry. In this limit, atomic tunneling is virtual, and only the atomic spins can exchange. We find a competition between symmetry breaking and liquid like disordered phases. Particularly interesting are valence bond states with bond centered magnetizations, situated between the ferromagnetic and conventional valence bond phases. In the framework of a mean-field theory, we calculate the phase diagram and identify an experimentally relevant parameter region where a homogeneous SU(4) symmetric Affleck-Kennedy-Lieb-Tasaki-like valence bond state is present.