Spin relaxation, Josephson effect and Yu-Shiba-Rusinov states in superconducting bilayer graphene

TL;DR

This paper investigates how magnetic impurities affect superconducting properties in bilayer graphene, revealing unique signatures in spin relaxation, Yu-Shiba-Rusinov states, and Josephson effects that depend on impurity resonance conditions.

Contribution

It introduces a combined analytical and numerical study of impurity-induced spectral features and superconducting transport in bilayer graphene, extending understanding beyond previous models.

Findings

Distinct spectral signatures for resonant and off-resonant impurities.

Doping and temperature influence Yu-Shiba-Rusinov states and supercurrent.

Unique superconducting signatures can discriminate impurity regimes.

Abstract

Bilayer graphene has two non-equivalent sublattices and, therefore, the same adatom impurity can manifest in spectrally distinct ways-sharp versus broad resonances near the charge neutrality-depending on the sublattice it adsorbs at. Employing Green's function analytical methods and the numerical Kwant package we investigate the spectral and transport interplay between the resonances and superconducting coherence induced in bilayer graphene by proximity to an s-wave superconductor. Analyzing doping and temperature dependencies of quasi-particle spin-relaxation rates, energies of Yu-Shiba-Rusinov states, Andreev spectra and the supercurrent characteristics of Josephson junctions we find unique superconducting signatures discriminating between resonant and off-resonant regimes. Our findings are in certain aspects going beyond the superconducting bilayer graphene and hold for generic s-wave superconductors functionalized by the resonant magnetic impurities.