Modeling Low- T C Transition-Edge Sensors Made of NS Bilayers: The Specific Interface Resistance

One way of making a transition-edge sensor (TES) is by utilizing the proximity effect, in which the $$T_{C}$$ of a superconducting film is reduced with a normal metal film in metallic contact. The $$T_{C}$$ of a bilayer TES can be estimated by solving the Usadel equations with given boundary conditions. The classical boundary conditions of a bilayer include a specific interface resistance being temperature-independent. In this paper, we will introduce a temperature-dependent specific interface resistance. By fitting the measured $$T_{C}$$ data of Ir/Au bilayers from the literature to a $$T_{C}$$ calculation model, we will compare the fit parameters and fit errors with the temperature-dependent specific interface resistance described in this work and with the classical temperature-independent specific interface resistance.