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

Abstract

Using a highly-sensitive home-made mutual-inductance technique, temperature profiles of the magnetic penetration depth $λ(T)$ in the optimally-doped $Sm_{1.85}Ce_{0.15}CuO_4$ thin films have been extracted. The low-temperature behavior of $λ(T)$ is found to be best-fitted by linear $Δλ(T)/λ(0)= \ln(2)k_BT/Δ_0$ and quadratic $Δλ(T)/λ(0)=Γ^{-1/2}Δ_0^{-3/2}T^2$ 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 $Δ_0/k_BT_C=2.07$ and $Γ/T_C=0.25(T_C/Δ_0)^3$ for the estimates of the nodal gap parameter and impurity scattering rate.