Link between magnetism and resistivity upturn in cuprates: a thermal conductivity study of La$_{2-x}$Sr$_x$CuO$_4$.
2019
A key unexplained feature of
cuprate superconductorsis the upturn in their normal state electrical resistivity $\rho(T)$ seen at low temperature inside the
pseudogapphase. 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
cuprateLa$_{2-x}$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-waveorder as observed in neutron scattering experiments on the same samples. This decrease of $\kappa_0/T$ with field is imposed by the
Wiedemann-Franz lawand 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
pseudogapphase of
cuprates. We discuss this scenario in the broader context of other
cuprates.
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