Tunneling spectroscopy for ferromagnet/superconductor junctions

TL;DR

This paper investigates how spin polarization, Fermi wavevector mismatch, and interfacial resistance influence tunneling spectroscopy in ferromagnet/superconductor junctions, revealing complex conductance features and conditions for zero bias peaks.

Contribution

It provides a comprehensive analysis of the effects of FWM, spin polarization, and pairing symmetry on conductance spectra in F/S junctions, including mixed pairing states.

Findings

FWM can enhance Andreev reflection and produce zero bias conductance peaks.

The pairing symmetry (s-wave, d-wave, or mixed) significantly affects the conductance features.

Spin polarization influences the low bias conductance, especially in the presence of FWM.

Abstract

In tunneling spectroscopy studies of ferromagnet/superconductor (F/S) junctions, the effects of spin polarization, Fermi wavevector mismatch (FWM) between the F and S regions, and interfacial resistance play a crucial role. We study the low bias conductance spectrum of these junctions, governed by Andreev reflection at the F/S interface. We consider both d- and s-wave superconductors as well as mixed states of the $d+is$ form. We present results for a range of values of the relevant parameters and find that a rich variety of features appears, depending on pairing state and other conditions. We show that in the presence of FWM, spin polarization can enhance Andreev reflection and give rise to a zero bias conductance peak for an s-wave superconductor.