Critical current of a superconductor measured via injection of spin-polarized carriers

Abstract

In this paper we report direct evidence of the suppression of critical current due to pair breaking in a superconducting micro-bridge when the measurement is carried out by injecting spin-polarized carriers instead of normal electrons. A thin layer of La_0.7Ca_0.3MnO₃ was used as the source of spin-polarized carriers. The micro-bridge was formed on the DyBa₂Cu₃O_7-δ thin film by photo-lithographic techniques. The design of our spin-injection device allowed us to inject spin-polarized carriers from the La_0.7Ca_0.3MnO₃ layer directly to the DyBa₂Cu₃O_7-δ micro-bridge (without any insulating buffer layer), making it possible to measure the critical current when polarized electrons alone are injected into the superconductor. Our results confirm the role of polarized carriers in breaking the Cooper pairs in the superconductor.