Identifying possible pairing states in Sr2RuO4 by tunneling spectroscopy

We examine the tunneling spectroscopy of three-dimensional normal-metal/Sr2RuO4 junctions as an experimental means to identify pairing symmetry in Sr2RuO4. In particular, we consider three different possible pairing states in Sr2RuO4: spin-singlet chiral d-wave, spin-triplet helical p-wave, and spin-nematic f-wave ones, all of which are consistent with recent nuclear-magnetic-resonance experiments [A. Pustogow et al., Nature (London) 574, 72 (2019)]. The Blonder-Tinkham-Klapwijk theory is employed to calculate the tunneling conductance, and the cylindrical two-dimensional Fermi surface of Sr2RuO4 is properly taken into account as an anisotropic effective mass and a cutoff in the momentum integration. It is pointed out that the chiral d-wave pairing state is inconsistent with previous tunneling conductance experiments along the c axis. We also find that the remaining candidates, the spin-triplet helical p-wave pairing state and the spin-nematic f-wave ones, can be distinguished from each other by the in-plane tunneling spectroscopy along the a and b axes.