Giant oscillatory Gilbert damping in superconductor/ferromagnet/superconductor junctions

TL;DR

This paper reports the experimental discovery of giant oscillatory Gilbert damping in superconductor/ferromagnet/superconductor junctions, revealing unconventional spin relaxation mechanisms linked to Andreev bound states and pi-junction properties.

Contribution

It provides the first experimental evidence of oscillatory Gilbert damping linked to zero-energy Andreev bound states in superconductor/ferromagnet/superconductor junctions.

Findings

Giant oscillatory Gilbert damping observed in Nb/NiFe/Nb junctions.

Damping linked to zero-energy Andreev bound states in pi-junctions.

Potential implications for quantum computing applications.

Abstract

Interfaces between materials with differently ordered phases present unique opportunities for exotic physical properties, especially the interplay between ferromagnetism and superconductivity in the ferromagnet/superconductor heterostructures. The investigation of zero- and pi-junctions has been of particular interest for both fundamental physical science and emerging technologies. Here, we report the experimental observation of giant oscillatory Gilbert damping in the superconducting Nb/NiFe/Nb junctions with respect to the NiFe thickness. This observation suggests an unconventional spin pumping and relaxation via zero-energy Andreev bound states that exist only in the Nb/NiFe/Nb pi-junctions, but not in the Nb/NiFe/Nb zero-junctions. Our findings could be important for further exploring the exotic physical properties of ferromagnet/superconductor heterostructures, and potential applications of ferromagnet pi-junctions in quantum computing, such as half-quantum flux qubits.