Electronic Inhomogeneity and Breakdown of the Universal Thermal Conductivity in Cuprate Superconductors

TL;DR

This study presents high-precision measurements of low-temperature thermal conductivity in cuprate superconductors, revealing a breakdown of the universal thermal conductivity due to electronic inhomogeneities, challenging existing theoretical predictions.

Contribution

It provides experimental evidence of the breakdown of universal thermal conductivity in cuprates, emphasizing the role of electronic inhomogeneities overlooked by standard theories.

Findings

Breakdown of universal thermal conductivity observed.

Electronic inhomogeneities significantly affect thermal transport.

Anisotropy in thermal conductivity linked to inhomogeneities.

Abstract

We report systematic, high-precision measurements of the low-T (down to 70 mK) thermal conductivity \kappa of YBa_{2}Cu_{3}O_{y}, La_{2-x}Sr_{x}CuO_{4} and Bi_{2}Sr_{2}CaCu_{2}O_{8+\delta}. Careful examinations of the Zn- and hole-doping dependences of the residual thermal conductivity \kappa_{0}/T, as well as the in-plane anisotropy of \kappa_{0}/T in Bi_{2}Sr_{2}CaCu_{2}O_{8+\delta}, indicate a breakdown of the universal thermal conductivity, a notable theoretical prediction for d-wave superconductors. Our results point to an important role of electronic inhomogeneities, that are not considered in the standard perturbation theory for thermal conductivity, in the under- to optimally-doped regime.