Manifestation of helical edge states as zero bias magneto-tunneling-conductance peaks in noncentrosymmetric superconductors

Helical edge states exist in the mixed spin singlet and triplet phase of a noncentrosymmetric superconductor (NCSS) when the pair amplitude (PA) in the negative helicity band, Δ-, is smaller than the PA in the positive helicity band, Δ+, i.e., when the PA in the triplet component is more than the same in the singlet component. We numerically determine energies of these edge states as a function of γ = Δ-/Δ+. The presence of these edge states is reflected in the tunneling process from a normal metal to an NCSS across a bias energy eV. (i) Angle resolved spin conductance (SC) obeying the symmetry gs(φ) = -gs(-φ) shows peaks when the bias energy equals the available quasiparticle edge state energy provided |eV|∼<Δ-. (ii) The total SC, Gs, is zero but modulates with eV for finite magnetic field H. (iii) The zero bias peaks of Gs and total charge conductance, Gc, at finite H split into two at finite eV for moderate H. (iv) At zero bias, Gc and Gs increase with H and show peaks at |H|∼γH0, where H0 is a characteristic field.