Reflectivity and Microwave Absorption in Crystals with Alternating Intrinsic Josephson Junctions

Abstract

We compute the frequency and magnetic field dependencies of the reflectivity $R(ω)$ in layered superconductors with two alternating intrinsic Josephson junctions with different critical current densities and quasiparticle conductivities for the electric field polarized along the c-axis. The parameter $α$ describing the electronic compressibility of the layers and the charge coupling of neighboring junctions was extracted for the SmLa$_{1-x}$Sr$_{x}$CuO$_{4-δ}$ superconductor from two independent optical measurements, the fit of the loss function $L(ω)$ at zero magnetic field and the magnetic field dependence of the peak positions in $L(ω)$. The experiments are consistent with a free electron value for $α$ near the Josephson plasma frequencies.