A model for excess Johnson noise in superconducting transition-edge sensors
Abigail L. Wessels, Kelsey M. Morgan, Johnathon D. Gard +8 more
Transition-edge sensors (TESs) are two-dimensional superconducting films utilized as highly sensitive detectors of energy or power. These detectors are voltage biased in the superconducting-normal transition where the film resistance is both finite and a strong function of temperature. Unfortunately, the amount of electrical noise observed in TESs exceeds the predictions of existing noise theories. We describe a possible mechanism for the unexplained excess noise, which we term "mixed-down noise." The source is Johnson noise, which is mixed down to low frequencies by Josephson oscillations in devices with a nonlinear current-voltage relationship. We derive an expression for the power spectral density of this noise and show that its predictions agree with measured data.
arXiv:1907.11343•Applied Physics Letters•May 17, 2021•18 citations