Quantum transport in semiconductor-superconductor microjunctions

A formula is derived that relates the conductance of a normal-metal–superconductor (NS) junction to the single-electron transmission eigenvalues. The formula is applied to a quantum point contact (yielding conductance quantization at multiples of 4${\mathit{e}}^2$/h), to a quantum dot (yielding a non-Lorentzian conductance resonance), and to quantum interference effects in a disordered NS junction (enhanced weak-localization and reflectionless tunneling through a potential barrier).