Thermal transport in the hidden-order state of URu$_{2}$Si$_{2}$

TL;DR

This study investigates thermal conductivity in URu$_{2}$Si$_{2}$'s normal state, revealing an unusual increase in thermal transport and Lorenz number upon ordering at 18K, indicating carrier disappearance and increased mean-free-paths.

Contribution

It provides new insights into the thermal transport behavior and carrier dynamics in the hidden-order state of URu$_{2}$Si$_{2}$, contrasting with typical magnetic ordering effects.

Findings

Thermal conductivity sharply increases below 18K.

Lorenz number is enhanced in the ordered state.

Carrier density decreases significantly in the hidden-order phase.

Abstract

We present a study of thermal conductivity in the normal state of the heavy-fermion superconductor URu$_{2}$Si$_{2}$. Ordering at 18K leads to a steep increase in thermal conductivity and (in contrast with all other cases of magnetic ordering in heavy-fermion compounds) to an enhancement of the Lorenz number. By linking this observation to several other previously reported features, we conclude that most of the carriers disappear in the ordered state and this leads to a drastic increase in both phononic and electronic mean-free-path.