NOISE MECHANISMS OF HIGH-TEMPERATURE SUPERCONDUCTORS AS INFRARED DETECTORS

Different noise mechanisms associated with the transport properties of high temperature superconductors are discussed. A theoretical model to predict the 1/f noise characteristics of high temperature superconductors to infrared excitations is proposed. Noise mechanisms are attributed to the effects of temperature variations on the quasiparticle fluctuations and kinetic characteristics of the superconductor. In the transition region the thermodynamic fluctuations modulate the conductivity of the sample causing voltage variations in the presence of a bias current contributing to the 1/f noise spectral power. The predictions of the model are compared to recent experimental measurements on YBaCuO epitaxial and single crystal thin films. The theoretical predictions in both cases are in general smaller than the measured values. We attribute the discrepancy to the effects of noise sources associated with the flux hopping process and thermally activated flux creep in the lattice structure which are not addressed in the current theory.