On the resistivity at low temperatures in electron-doped cuprate superconductors

TL;DR

This study investigates the low-temperature resistivity and magnetoresistance in underdoped electron-doped cuprate superconductors, revealing behaviors inconsistent with standard models and suggesting magnetic droplets influence resistivity near antiferromagnetic phases.

Contribution

It provides new experimental data on resistivity and magnetoresistance at ultra-low temperatures in underdoped cuprates, challenging existing theories and proposing magnetic droplets as a key factor.

Findings

Resistivity saturates at very low temperatures under magnetic fields.

Magnetoresistance cannot be explained by superconductor-insulator transition or Kondo effect.

Magnetic droplets may induce negative magnetoresistance and resistivity upturns.

Abstract

We measured the magnetoresistance as a function of temperature down to 20mK and magnetic field for a set of underdoped PrCeCuO (x=0.12) thin films with controlled oxygen content. This allows us to access the edge of the superconducting dome on the underdoped side. The sheet resistance increases with increasing oxygen content whereas the superconducting transition temperature is steadily decreasing down to zero. Upon applying various magnetic fields to suppress superconductivity we found that the sheet resistance increases when the temperature is lowered. It saturates at very low temperatures. These results, along with the magnetoresistance, cannot be described in the context of zero temperature two dimensional superconductor-to-insulator transition nor as a simple Kondo effect due to scattering off spins in the copper-oxide planes. We conjecture that due to the proximity to an antiferromagnetic phase magnetic droplets are induced. This results in negative magnetoresistance and in an upturn in the resistivity.