Dynamical Jahn-Teller Effect in Spin-Orbital Coupled System

TL;DR

This paper investigates the dynamical Jahn-Teller effect in a spin-orbital system on a honeycomb lattice, revealing a spin-orbital resonant state that may explain spin-liquid behavior in Ba3CuSb2O9.

Contribution

The study derives an effective vibronic Hamiltonian incorporating superexchange and DJT effects, identifying a novel spin-orbital resonant state in the system.

Findings

DJT effect induces a spin-orbital resonant state.

Resonant state lies between orbital order and antiferromagnetic order.

Proposes a scenario for spin-liquid behavior in Ba3CuSb2O9.

Abstract

Dynamical Jahn-Teller (DJT) effect in a spin-orbital coupled system on a honeycomb lattice is examined, motivated from recently observed spin-liquid behavior in Ba$_3$CuSb$_2$O$_9$. An effective vibronic Hamiltonian, where the superexchange interaction and the DJT effect are taken into account, is derived. We find that the DJT effect induces a spin-orbital resonant state where local spin-singlet states and parallel orbital configurations are entangled with each other. This spin-orbital resonant state is realized in between an orbital ordered state, where spin-singlet pairs are localized, and an antiferromagnetic ordered state. Based on the theoretical results, a possible scenario for Ba$_3$CuSb$_2$O$_9$ is proposed.