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

An understanding of the normal state in the high-T_c superconducting cuprates is crucial to the 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. In electron-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. We report measurements of the low temperature normal state magnetoresistance (MR) of the n-type cuprate system (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). This unconventional behavior suggests that magnetic fields probe the same physics that gives rise to the anomalous low-temperature linear-in-T resistivity. The magnitude of the linear MR decreases as T_c decreases and goes to zero at the end of the superconducting dome (x ~0.175) above which a conventional quadratic MR is found. we discuss the correlation between Linear-in-T and Linear-in-H resistivity with the superconductivity.