Pulsed terahertz‐beam spectroscopy as a probe of the thermal and quantum response of YBa2Cu3O7−δ superfluid

Abstract

Pulsed terahertz spectroscopy is used to determine the superfluid response of a YBa2Cu3O7−δ film under both thermal and optical stimulation. The coherent, time‐domain technique is used in a novel configuration to directly measure the complex conductivity of the film versus temperature and continuous‐wave laser illumination. At 0.6 Tc, the superfluid shows an identical response regardless of whether the stimulus is thermal or optical. This contrasts with the behavior of the superfluid at 0.26 Tc, where dramatic differences are observed depending on whether the sample is heated or subjected to optical illumination. It is suggested that these differences arise from an enhanced contribution due to quantum effects, and thus also from a strong temperature dependence of the quasiparticle recombination time at low temperatures. © 1995 American Institute of Physics.