Cooper-Pair Spin Current in a Strontium Ruthenate Heterostructure

TL;DR

This paper proposes a novel heterostructure of SrRuO3 and Sr2RuO4 to generate and electrically control spin-triplet Cooper-pair spin currents, offering a new way to observe spin superfluidity and signatures of triplet superconductivity.

Contribution

It introduces a new heterostructure platform for realizing and controlling spin-triplet supercurrents and spin superfluidity in superconductors.

Findings

Demonstrates long-range spin valve in the heterostructure

Shows electrical driving of collective spin modes

Proposes transport signatures of triplet superconductivity

Abstract

It has been recognized that the condensation of spin-triplet Cooper pairs requires not only the broken gauge symmetry but also the spin ordering as well. One consequence of this is the possibility of the Cooper-pair spin current analogous to the magnon spin current in magnetic insulators, the analogy also extending to the existence of the Gilbert damping of the collective spin-triplet dynamics. The recently fabricated heterostructure of the thin film of the itinerant ferromagnet SrRuO3 on the bulk Sr2RuO4, the best-known candidate material for the spin-triplet superconductor, offers a promising platform for generating such spin current. We will show how such heterostructure allows us to not only realize the long-range spin valve but also electrically drive the collective spin mode of the spin-triplet order parameter. Our proposal represents both a new realization of the spin superfluidity and a transport signature of the spin-triplet superconductivity.