Temperature-dependence of spin-polarized transport in ferromagnet / unconventional superconductor junctions

TL;DR

This paper theoretically investigates how temperature affects spin-polarized tunneling conductance in ferromagnet/unconventional superconductor junctions, revealing distinctive features related to pairing symmetry and magnetic orientation.

Contribution

It provides a detailed analysis of temperature-dependent conductance in various superconductor pairing symmetries and ferromagnetic orientations, highlighting potential methods to determine spin polarization and d-vector direction.

Findings

Zero-energy Andreev bound states influence ZBC temperature dependence in d-wave junctions.

Conductance varies significantly with magnetic moment direction and pairing symmetry in p-wave junctions.

Characteristic conductance features can reveal spin polarization levels and superconductor pairing orientation.

Abstract

Tunneling conductance in ferromagnet / unconventional superconductor junctions is studied theoretically as a function of temperatures and spin-polarization in feromagnets. In d-wave superconductor junctions, the existence of a zero-energy Andreev bound state drastically affects the temperature-dependence of the zero-bias conductance (ZBC). In p-wave triplet superconductor junctions, numerical results show a wide variety in temperature-dependence of the ZBC depending on the direction of the magnetic moment in ferromagnets and the pairing symmetry in superconductors such as $p_{x}$, $p_{y}$ and $p_{x}+ip_{y}$-wave pair potential. The last one is a promising symmetry of Sr$_2$RuO$_4$. From these characteristic features in the conductance, we may obtain the information about the degree of spin-polarization in ferromagnets and the direction of the $d$-vector in triplet superconductors.