Microwave Electrodynamics of Electron-Doped Cuprate Superconductors

We report microwave cavity perturbation measurements of the temperature dependence of the penetration depth, $\lambda \left(T\right)$, and conductivity, $\sigma \left(T\right)$ of ${\mathrm{Pr}}_{2-x}{\mathrm{Ce}}_x{\mathrm{CuO}}_{4-\delta }$ (PCCO) crystals, as well as parallel-plate resonator measurements of $\lambda \left(T\right)$ in PCCO thin films. Penetration depth measurements are also presented for a ${\mathrm{Nd}}_{2-x}{\mathrm{Ce}}_x{\mathrm{CuO}}_{4-\delta }$ (NCCO) crystal. We find that $\Delta \lambda \left(T\right)$ has a power-law behavior for $T<\mathrm{}{T}_c/3$, and conclude that the electron-doped cuprate superconductors have nodes in the superconducting gap. Furthermore, using the surface impedance, we have derived the real part of the conductivity, ${\sigma }_1\left(T\right)$, below $T_c$ and found a behavior similar to that observed in hole-doped cuprates.