Weak antiferromagnetism and dimer order in quantum systems of coupled tetrahedra

TL;DR

This paper investigates the complex phases of a quantum spin model on coupled tetrahedra, revealing weak antiferromagnetic and dimer ordered states with unique symmetry-breaking and magnetic properties.

Contribution

It uncovers the existence of weak antiferromagnetic order and dimer states induced by interactions and magnetic fields in a coupled tetrahedra system, highlighting novel quantum phases.

Findings

Identification of non-magnetic dimer order

Discovery of weak antiferromagnetic order with small moments

External fields induce coexisting magnetic and dimer correlations

Abstract

We analyze the phases of an S=1/2 spin model on a lattice of coupled tetrahedra. The presence of both Heisenberg and antisymmetric, Dzyaloshinsky-Moriya interactions can lead to two types of symmetry-broken states: non-magnetic dimer order and, unexpectedly, exotic 4 sub-lattice weak antiferromagnetic order - a state with a generically small ordered moment and non-zero chirality. External magnetic field also induces weak antiferromagnetism co-existing with strong dimer correlations in the ground state. These states are formed as a result of broken Ising symmetries and exhibit a number of unusual properties.