Observation of a Far-Infrared Sphere Resonance in Superconducting La(2-x)Sr(x)CuO(4-y) Particles

摘要

Far-infrared (FIR) spectroscopic data on high-Tc single crystals in the superconducting state have been interpreted as evidence for a large energy gap, a BCS-type gap, or no gap at all. The optical properties of crystals of variable quality make it difficult to conclude whether or not the peak observed in the ratio of the FIR reflectivity of the a-b plane of YBa2CuO(7-y) in the superconducting state to that of the normal state should be interpreted as evidence for the energy gap or as evidence for a zero crossing of the real part of the dielectric function. The gap of La(2-x)Sr(x)CuO(4-y) is even less well determined because it has been difficult to grow single crystals at the Sr doping which produces the highest Tc's. The optical properties of superconducting sintered La(2-x)Sr(x)CuO(4-y) have been analyzed in some detail but the excess absorption in the superconducting state associated with transport between grains obscures the determination of a true gap signature. Keywords: Superconductors, Reprints. (jes)