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

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${}_4$.

12 pages, 7 figures. There is also a supplementary (not uploaded)