Polar Dynamics at the Jahn-Teller Transition in Ferroelectric GaV4S8

TL;DR

This study investigates the polar dynamics associated with the Jahn-Teller driven ferroelectric transition in GaV4S8 using dielectric spectroscopy across THz to GHz frequencies, revealing critical fluctuations and a significant relaxation time jump.

Contribution

It combines THz and MHz-GHz spectroscopy to detect coupled orbital and polar fluctuations and characterizes their temperature-dependent relaxation dynamics in GaV4S8.

Findings

Relaxation time increases near the transition temperature.

Enormous five-order magnitude jump in relaxation time at the transition.

Polar fluctuations reflect orbital dynamics at the Jahn-Teller transition.

Abstract

We present a dielectric spectroscopy study of the polar dynamics linked to the orbitally driven ferroelectric transition in the skyrmion host GaV4S8. By combining THz and MHz-GHz spectroscopy techniques, we succeed in detecting the relaxational dynamics arising from coupled orbital and polar fluctuations in this material and traced its temperature dependence in the paraelectric as well as in the ferroelectric phase. The relaxation time significantly increases when approaching the critical temperature from both sides of the transition. It is natural to assume that these polar fluctuations map the orbital dynamics at the Jahn-Teller transition. Due to the first-order character of the orbital-ordering transition, the relaxation time shows an enormous jump of about five orders of magnitude at the polar and structural phase transition.