Finite frequency noise of a superconductor/ferromagnet quantum point contact

TL;DR

This paper calculates the finite-frequency current noise in a superconductor-ferromagnet quantum point contact, showing how spin-dependent phase shifts influence the noise and proposing it as a tool to probe scattering properties.

Contribution

It introduces a detailed analysis of finite-frequency noise in SF QPCs, highlighting the impact of SDIPS and suggesting experimental applications.

Findings

Noise steps occur at frequencies/voltages linked to SDIPS

Steps are observable at accessible temperatures and frequencies

Finite frequency noise can characterize scattering properties

Abstract

We have calculated 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 (SDIPS) acquired by electrons upon reflection on the QPC. For a weakly transparent QPC, noise steps appear at frequencies or voltages determined directly by the SDIPS. 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.