Finite Frequency Noise of a Superconductor-Ferromagnet Quantum Point Contact

Abstract

We calculate the finite-frequency current noise of a superconductor-ferromagnet quantum point contact (SF QPC). This signal is qualitatively affected by the spin dependence of interfacial phase shifts acquired by electrons upon reflection on the QPC. For a weakly transparent QPC, noise steps appear at frequencies or voltages determined directly by the spin dependence of interfacial phase shifts. These steps can occur at experimentally accessible temperatures and frequencies. Finite-frequency noise is thus a promising tool to characterize the scattering properties of a SF QPC.