Theory of tunneling spectroscopy of normal metal/ferromagnet/spin-triplet superconductor junctions

TL;DR

This paper models the tunneling conductance in a normal metal/ferromagnet/spin-triplet superconductor junction to distinguish between chiral and helical p-wave pairing symmetries, aiding in identifying the pairing state of Sr$_{2}$RuO$_{4}$.

Contribution

It introduces a theoretical analysis comparing chiral and helical p-wave pairings in a ferromagnet/superconductor junction using an extended BTK formalism.

Findings

Different voltage dependencies for chiral and helical p-wave pairings.

Identical conductance when the d-vector is perpendicular to magnetization.

Guidance for experimental identification of pairing symmetry.

Abstract

We study the tunneling conductance of a ballistic normal metal / ferromagnet / spin-triplet superconductor junction using the extended Blonder-Tinkham-Klapwijk formalism as a model for a $c$-axis oriented Au / SrRuO$_{3}$ / Sr$_{2}$RuO$_{4}$ junction. We compare chiral $p$-wave (CPW) and helical $p$-wave (HPW) pair potentials, combined with ferromagnet magnetization directions parallel and perpendicular to the interface. For fixed $\theta_{M}$, where $\theta_{M}$ is a direction of magnetization in the ferromagnet measured from the $c$-axis, the tunneling conductance of CPW and HPW clearly show different voltage dependencies. It is found that the cases where the $d$-vector is perpendicular to the magnetization direction (CPW with $\theta_{M} = \pi/2$ and HPW with $\theta_{M} = 0$) are identical. The obtained results serve as a guide to determine the pairing symmetry of the spin-triplet superconductor Sr$_{2}$RuO$_{4}$.