Energy Dependence of Current Noise in Superconducting/Normal Metal Junctions

Interference of electronic waves undergoing Andreev reflection in diffusive conductors determines the energy profile of the conductance on the scale of the Thouless energy. A similar dependence exists in the current noise, but its behavior is known only in a few limiting cases. We consider a metallic diffusive wire connected to a superconducting reservoir through an interface characterized by an arbitrary distribution of channel transparencies. Within the quasiclassical theory for current fluctuations we provide a general expression for the energy dependence of the current noise.

Figure 1

Energy dependence of the conductance and of the differential Fano factor when the wire and the interface have the same conductance ($G_D=G_B$) for different values of $\Gamma ={\Gamma }_n$ [25]. The dashed lines correspond to the universal distribution $\{{\Gamma }_n\}$ for disordered interfaces.