Spin Transport and Nonequilibrium Superconductivity in YBa2Cu3O7-δ

Author: Huang, Zhao

Year: 2000

Degree: Senior thesis (Major)

Advisor: Yeh, Nai-Chang

Option: Physics

DOI: 10.7907/X0B4-8905

Abstract

Our studies of YBa₂Cu₃O_7-δ under the injection of spin-polarized quasi-particles have yielded new spin transport information along the c-axis as well as signatures of non-equilibrium effects. We have found a surprisingly strong divergence of the spin diffusion lengths at the transition temperature T_c which suggests a new model for the suppression of the critical current I_c under the influence of excess spin. We have discovered at low temperatures quasiparticle distribution effects due to the perturbation of an external injection. We report preliminary results for the search for "preformed" Cooper pairs above T_c. And finally we present initial spin injection transport studies in a microwave background from which we can estimate an upper bound on the electron-phonon scattering time and Cooper pair recombination time in YBCO.