Dielectric Evidence for Possible Type-II Multiferroicity in alpha-RuCl3

TL;DR

This study shows that dielectric measurements in alpha-RuCl3 reveal magnetic transitions and suggest it may be a type-II multiferroic, with dielectric constant serving as a probe for magnetic order.

Contribution

It provides the first dielectric evidence indicating alpha-RuCl3 could be a type-II multiferroic, linking dielectric behavior to magnetic phase transitions.

Findings

Dielectric constant drops at magnetic transition temperature T_N.

Drop in dielectric constant tracks T_N with increasing magnetic field.

Behavior changes above critical field H_c ~ 7.5 T, indicating a quantum phase transition.

Abstract

$\alpha$-RuCl$_3$ is a Mott insulator with a honeycomb lattice with strong spin-orbit coupling. We report dielectric measurements on $\alpha$-RuCl$_3$ single crystals under field. At zero field, the dielectric constant, $\epsilon$, drops rapidly when cooled through the magnetic transition temperature T$_N$. With increasing field, the onset of the drop in $\epsilon$ tracks the T$_N$. Such behavior is absent with field above a critical value H$_c$ ~ 7.5 T, indicating the onset of a quantum phase transition. Our data suggest that the dielectric constant can be used as a probe of magnetic ordering in $\alpha$-RuCl$_3$, and $\alpha$-RuCl$_3$ is a possible type-II multiferroics.