Abstract
We have measured the complex conductivity of single-crystal thin films using coherent THz spectroscopy. We obtain directly the London penetration depth, the plasma frequency , and the quasiparticle scattering rate 1/τ. We find that 1/τ drops rapidly with temperature below in all the superconducting samples, implying that this is a signature of high- superconductivity. decreases with increasing x, indicating that Pr takes mobile carriers from the CuO planes. Both the THz and dc conductivity yield evidence for the opening of a spin gap above .
DOI:https://doi.org/10.1103/PhysRevB.50.9672
©1994 American Physical Society