Minimal Conductance Quantization in a Normal-Metal/Unconventional-Superconductor Junction

We discuss the minimum value of the zero-bias differential conductance in a normal-metal/unconventional-superconductor junction. A numerical simulation demonstrates that the zero-bias conductance is quantized at $$(4e^2/h) N_\mathrm {ZES}$$ in the limit of strong impurity scatterings in the normal-metal. The integer $$N_\mathrm {ZES}$$ represents the number of perfect transmission channels through the junction. By focusing on the chiral symmetry of Hamiltonian, we prove the existence of $$N_\mathrm {ZES}$$ -fold degenerate resonant states in the dirty normal segment.