Link between magnetism and resistivity upturn in cuprates: a thermal conductivity study of La$_{2-x}$Sr$_x$CuO$_4$

TL;DR

This study links the resistivity upturn in cuprates' pseudogap phase to magnetic order, using thermal conductivity measurements in La$_{2-x}$Sr$_x$CuO$_4$ to reveal how magnetism influences electronic transport.

Contribution

It provides direct experimental evidence connecting magnetic order with resistivity behavior in cuprates through thermal conductivity analysis.

Findings

Resistivity upturn correlates with spin density-wave order.

Thermal conductivity decreases with magnetic field in certain doping levels.

Magnetism influences the normal state properties of cuprates.

Abstract

A key unexplained feature of cuprate superconductors is the upturn in their normal state electrical resistivity $\rho(T)$ seen at low temperature inside the pseudogap phase. We examined this issue via measurements of the thermal conductivity $\kappa(T)$ down to 50 mK and in fields up to 17 T on the cuprate La$_{2-x}$Sr$_x$CuO$_4$ at dopings $p = 0.13$, 0.136, 0.143 and 0.18. At $p$ = 0.136, 0.143, and 0.18, we observe an initial increase of the electronic thermal conductivity $\kappa_0/T$ as a function of field, as expected in a $d$-wave superconductor. For $p$ = 0.136 and 0.143, further increasing the field then leads to a decrease of $\kappa_0/T$, which correlates with the onset of spin density-wave order as observed in neutron scattering experiments on the same samples. This decrease of $\kappa_0/T$ with field is imposed by the Wiedemann-Franz law and the high value of the resistivity in the high-field normal state of these samples. Our study therefore provides a direct link between magnetism and the resistivity upturn in the pseudogap phase of cuprates. We discuss this scenario in the broader context of other cuprates.