Phonon thermal conductivity in doped $\rm\bf La_2CuO_4$: Relevant scattering mechanisms

TL;DR

This study investigates phonon thermal conductivity in doped La2CuO4, identifying impurity scattering and soft phonons as key mechanisms, and finds no significant role for stripe correlations in phonon peak suppression.

Contribution

It provides detailed measurements of thermal conductivity in doped La2CuO4 and clarifies the dominant phonon scattering mechanisms, contrasting with related compounds.

Findings

Impurity scattering and soft phonons dominate phonon scattering in La2-xSrxCuO4.

The phonon peak decreases with increasing Sr content.

Stripe correlations do not significantly suppress phonon thermal conductivity.

Abstract

Results of in-plane and out-of-plane thermal conductivity measurements on $\rm La_{1.8-x}Eu_{0.2}Sr_xCuO_4$ ($0\leq x\leq0.2$) single crystals are presented. The most characteristic features of the temperature dependence are a pronounced phonon peak at low temperatures and a steplike anomaly at $T_{LT}$, i.e., at the transition to the low temperature tetragonal phase (LTT-phase), which gradually decrease with increasing Sr-content. Comparison of these findings with the thermal conductivity of $\rm La_{2-x}Sr_xCuO_4$ and $\rm La_2NiO_4$ clearly reveals that in $\rm La_{2-x}Sr_xCuO_4$ the most effective mechanism for phonon scattering is impurity-scattering (dopants), as well as scattering by soft phonons that are associated with the lattice instability in the low temperature orthorhombic phase (LTO-phase). There is no evidence that stripe correlations play a major role in suppressing the phonon peak in the thermal conductivity of $\rm La_{2-x}Sr_xCuO_4$.