Correlation between scale-invariant normal state resistivity and superconductivity in an electron-doped cuprate

TL;DR

This study reveals a correlation between scale-invariant resistivity and superconductivity in electron-doped cuprates, showing that quantum critical fluctuations influence the normal state and superconducting properties.

Contribution

It demonstrates a direct link between linear magnetoresistance and the quantum critical point in electron-doped cuprates, providing new insights into the normal state and superconductivity.

Findings

Linear-in-field magnetoresistance above the QCP

MR magnitude decreases with Tc and vanishes at the end of the superconducting dome

Conventional quadratic MR observed beyond the superconducting dome

Abstract

An understanding of the normal state in the high-temperature superconducting cuprates is crucial to the ultimate understanding of the long-standing problem of the origin of the superconductivity itself. This so-called strange metal state is thought to be associated with a quantum critical point (QCP) hidden beneath the superconductivity(1,2). In electron-doped cuprates in contrast to hole-doped cuprates it is possible to access the normal state at very low temperatures and low magnetic fields to study this putative QCP and to probe the T~0 K state of these materials(3,4). We report measurements of the low temperature normal state magnetoresistance (MR) of the n-type cuprate system La2-xCexCuO4 (LCCO) and find that it is characterized by a linear-in-field behavior, which follows a scaling relation with applied field and temperature, for doping (x) above the putative QCP (x= 0.14)(5). This unconventional behavior suggests that magnetic fields probe the same physics that gives rise to the anomalous low-temperature linear-in-T resistivity(4). The magnitude of the linear MR decreases as Tc decreases and goes to zero at the end of the superconducting dome (x ~0.175) above which a conventional quadratic MR is found. These results show that there is a strong correlation between the quantum critical excitations of the strange metal state and the high-Tc superconductivity.