Probing pairing symmetry of Sm_{1.85}Ce_{0.15}CuO_4 via highly-sensitive voltage measurements: Evidence for strong impurity scattering

TL;DR

This study uses sensitive voltage measurements to analyze the magnetic penetration depth in optimally-doped Sm_{1.85}Ce_{0.15}CuO_4 thin films, revealing d-wave pairing symmetry influenced by strong impurity scattering.

Contribution

It provides experimental evidence for d-wave pairing symmetry in electron-doped cuprates through detailed penetration depth measurements and analysis of impurity effects.

Findings

Linear temperature dependence of penetration depth at low T

Quadratic behavior above 0.22T_C indicating impurity scattering

Estimated nodal gap and impurity scattering rate values

Abstract

Using a highly-sensitive home-made mutual-inductance technique, temperature profiles of the magnetic penetration depth $\lambda (T)$ in the optimally-doped $Sm_{1.85}Ce_{0.15}CuO_4$ thin films have been extracted. The low-temperature behavior of $\lambda (T)$ is found to be best-fitted by linear $\Delta \lambda (T)/\lambda (0)= \ln(2)k_BT/\Delta_0$ and quadratic $\Delta \lambda (T)/\lambda (0)=\Gamma ^{-1/2}\Delta_0^{-3/2}T^2$ laws above and below $T=0.22T_C$, respectively, which clearly indicates the presence of d-wave pairing mechanism dominated by strong paramagnetic scattering at the lowest temperatures. The best fits produce $\Delta_0/k_BT_C=2.07$ and $\Gamma /T_C=0.25(T_C/\Delta_0)^3$ for the estimates of the nodal gap parameter and impurity scattering rate.