Theory of tunneling conductance of anomalous Rashba metal/superconductor junctions

We theoretically study charge conductance in anomalous Rashba metal (ARM)/superconductor junctions for various types of pairing symmetries in a superconductor. The exotic state dubbed ARM, where one of the spin-resolved Fermi surfaces is absent, is realized when the chemical potential is tuned both in the presence of Rashba spin-orbit interaction (RSOI) and an exchange field. Although a fully polarized ferromagnet metal (FPFM) is also a system in which the electron's spin degrees of freedom are reduced by half, the electrons in an ARM have features that are distinct from those in a FPFM. For the ARM/spin-singlet superconductor junctions, the obtained tunneling conductance within the bulk energy gap is enhanced with the increase in magnitude of the RSOI. In particular, in ARM/dxy-wave superconductor junctions, the zero-bias conductance peak is enhanced due to the presence of the RSOI. For ARM/px-wave superconductor junctions, the condition of the existence of the zero-bias conductance peak is significantly sensitive to the direction of the d vector of the px-wave superconductor. Furthermore, the obtained conductance in ARM/chiral p-wave superconductor junctions shows different behaviors as compared to those in ARM/helical p-wave superconductor junctions. This feature serves as a guide to determine the spin structure of a Cooper pair in the spin-triplet superconductor Sr2RuO4.