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

Abstract

In this paper we report direct evidence of the suppression of critical currentdue to pair breaking in a superconducting micro-bridge when the measurement iscarried out by injecting spin-polarized carriers instead of normal electrons.A thin layer of La0.7Ca0.3MnO3 was used as thesource of spin-polarized carriers. The micro-bridge was formed on the DyBa2Cu3O7-δ thin film by photo-lithographictechniques. The design of our spin-injection device allowed us to injectspin-polarized carriers from the La0.7Ca0.3MnO3layer directly to the DyBa2Cu3O7-δ micro-bridge(without any insulating buffer layer), making it possible to measure thecritical current when polarized electrons alone are injected into thesuperconductor. Our results confirm the role of polarized carriers in breakingthe Cooper pairs in the superconductor.