Significant thermal Hall effect in the 3$d$ cobalt Kitaev system $Na_2Co_2TeO_6$

TL;DR

This study reports a significant thermal Hall effect in the Kitaev candidate material Na2Co2TeO6, revealing insights into charge-neutral quasiparticles and magnetic field effects in quantum spin liquids.

Contribution

It provides the first observation of a notable thermal Hall effect in a 3d cobalt Kitaev system, expanding understanding of quantum spin liquids and thermal transport phenomena.

Findings

Thermal Hall conductivity persists up to 150 K.

Distinct magnetic field dependence of thermal conductivity below and above T_N.

Complex field dependence of thermal transport below T_N.

Abstract

Kitaev physics has recently attracted attention in condensed matter for its anticipated novel quantum spin liquid state. The thermal transport measurement is crucial for probing the novel features of charge-neutral quasiparticles. In this letter, we report a significant thermal Hall effect in $Na_2Co_2TeO_6$ (NCTO), a Kitaev quantum spin liquid candidate, when the magnetic field is applied along the out-of-plane direction of the honeycomb plane. The thermal conductivity ($\kappa_{xx}$) and thermal Hall conductivity ($\kappa_{xy}$) in NCTO reveal distinct magnetic field dependences below and above the Neel temperature ($T_N$) of 27 K. For $T>T_N$, $\kappa_{xx}$ has a monotonic decrease in the field dependence, while $\kappa_{xy}$ persists up to $T^*$ = 150 K. On the other hand, both $\kappa_{xx}$ and $\kappa_{xy}$ exhibit complex field dependence for $T<T_N$.