Phase-controlled spin and charge currents in superconductor-ferromagnet hybrids

TL;DR

This paper explores how voltage biasing in superconductor-ferromagnet hybrids can generate, control, and detect equal-spin triplet Cooper pairs and spin currents, revealing new ways to manipulate quantum states in hybrid systems.

Contribution

It demonstrates that voltage biasing induces triplet correlations and enables control and detection of equal-spin triplet pairs in superconductor-ferromagnet hybrids.

Findings

Voltage biasing induces superconducting triplet correlations.

Unequal spin-mixing conductances produce detectable equal-spin triplet correlations.

The device allows generation, control, and detection of equal-spin triplet Cooper pairs.

Abstract

We investigate spin-dependent quasiparticle and Cooper-pair transport through a central node interfaced with two superconductors and two ferromagnets. We demonstrate that voltage biasing of the ferromagnetic contacts induces superconducting triplet correlations on the node and reverses the supercurrent flowing between the two superconducting contacts. We further find that such triplet correlations can mediate a tunable spin current flow into the ferromagnetic contacts. Our key finding is that unequal spin-mixing conductances for the two interfaces with the ferromagnets result in equal-spin triplet correlations on the node, detectable via a net charge current between the two magnets. Our proposed device thus enables the generation, control, and detection of the typically elusive equal-spin triplet Cooper pairs.