Critical current in a spin injection device

Abstract

We report on direct evidence of the suppression of critical current due to pair-breaking in a superconducting microbridge 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 microbridge was formed on the DyBa₂Cu₃O_7−δ thin film by photolithographic 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 microbridge (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.