From non-metal to strange metal at the stripe-percolation transition in La$_{2-x}$Sr$_x$CuO$_4$

TL;DR

This paper investigates the transition from non-metallic to strange metallic behavior in La$_{2-x}$Sr$_x$CuO$_4$, linking it to a first-order transition influenced by stripe correlations and disorder, with implications for understanding high-temperature superconductivity.

Contribution

It provides experimental evidence for a doping-induced transition in La$_{2-x}$Sr$_x$CuO$_4$ and models the role of stripe correlations and disorder in this transition.

Findings

Strange-metal behavior appears for doping levels above p* ~ 0.19.

Below p*, charge and spin stripe correlations percolate across CuO2 planes.

Above p*, stripe correlations are confined to isolated puddles.

Abstract

The nature of the normal state of cuprate superconductors continues to stimulate considerable speculation. Of particular interest has been the linear temperature dependence of the in-plane resistivity in the low-temperature limit, which violates the prediction for a Fermi liquid. We present measurements of anisotropic resistivity in La$_{2-x}$Sr$_x$CuO$_4$ that confirm the strange-metal behavior for crystals with doped-hole concentration $p=x > p^\ast \sim 0.19$ and contrast with the non-metallic behavior for $p<p^\ast$. We propose that the changes at $p^\ast$ are associated with a first-order transition from doped Mott insulator to conventional metal; the transition appears as a crossover due to intrinsic dopant disorder. We consider results from the literature that support this picture; in particular, we present a simulation of the impact of the disorder on the first-order transition and the doping dependence of stripe correlations. Below $p^\ast$, the strong electronic interactions result in charge and spin stripe correlations that percolate across the CuO$_2$ planes; above $p^\ast$, residual stripe correlations are restricted to isolated puddles. We suggest that the $T$-linear resistivity results from scattering of quasiparticles from antiferromagnetic spin fluctuations within the correlated puddles. This is a modest effect compared to the case at $p<p^\ast$, where there data suggest that there are no coherent quasiparticles in the normal state.