Exchange and spin Jahn-Teller distortions for a triangular cluster of spin-1/2

TL;DR

This paper investigates how magnetoelastic coupling influences the ground state degeneracy of a spin-1/2 triangular cluster, revealing static and dynamic Jahn-Teller effects and their impact on energy stabilization.

Contribution

It demonstrates the distinct roles of static and dynamical displacements in lifting degeneracy and quantifies the energy differences due to quantum fluctuations.

Findings

Static displacement lifts ground state degeneracy via exchange dependence.

Dynamical displacement does not lift degeneracy but causes spontaneous distortion.

Quantum fluctuations double the energy stabilization compared to static theory.

Abstract

We study the effects of magnetoelastic coupling on the degenerate ground state of the spin-1/2 antiferromagnetic Heisenberg model for the regular triangular spin cluster. Static displacement of spins spontaneously lifts the degeneracy of the ground state through the distance dependence of exchange coupling, i.e., a spin Jahn-Teller mechanism takes place. On the other hand, dynamical displacement does not lift the degeneracy, though the cluster distorts spontaneously. The energy decrease obtained by dynamical theory is twice as large as that obtained by static theory because of quantum fluctuation.