Influence of carbon substitution on the heat transport in single crystalline MgB2

TL;DR

This study investigates how carbon substitution affects heat transport in single-crystalline MgB2, revealing reduced electronic thermal conductivity and the validity of the Wiedemann-Franz law at low temperatures for certain compositions.

Contribution

It provides new experimental data on thermal conductivity in carbon-substituted MgB2 and shows how impurity scattering influences heat transport mechanisms.

Findings

Carbon substitution reduces electronic heat transport.

Phonon thermal conductivity remains relatively unaffected by impurities.

Wiedemann-Franz law holds for Mg(B0.94C0.06)2 at low temperatures.

Abstract

We report data on the thermal conductivity \kappa(T,H) in the basal plane of hexagonal single-crystalline and superconducting Mg(B_{1-x}C_x)_2 (x= 0.03, 0.06) at temperatures between 0.5 and 50 K, and in external magnetic fields H between 0 and 50 kOe. The substitution of carbon for boron leads to a considerable reduction of the electronic heat transport, while the phonon thermal conductivity seems to be much less sensitive to impurities. The introduction of carbon enhances mostly the intraband scattering in the \sigma-band. In contrast to the previously observed anomalous behavior of pure MgB$_2$, the Wiedemann-Franz law is valid for Mg(B_0.94 C_0.06)_2 at low temperatures.