Demonstration of Weak-Link Physics in the Dynamical Response of Transition-Edge Sensors

TL;DR

This paper combines theoretical modeling and experimental measurements to demonstrate that weak-link physics, related to Josephson phenomena, governs the dynamical response of transition-edge sensors, explaining their noise characteristics.

Contribution

It introduces a Fokker-Planck based framework that links weak-link physics to TES response and noise, providing new insights into their operation and noise sources.

Findings

Excellent agreement between theory and experiment on dynamic resistance

Weak-link physics identified as key to TES operation

Framework enables analysis of excess noise in TES

Abstract

We theoretically predict and experimentally observe the onset of weak-link physics in the dynamical response of transition edge sensors (TES). We develop a theoretical framework based on a Fokker-Planck description that incorporates both the TES electrical response, stemming from Josephson phenomena, and the electrothermal effects due to coupling to a thermal bath. Our measurements of a varying dynamic resistance are in excellent agreement with our theory, thereby establishing weak-link phenomena as the main mechanism underlying the operation of TES. Furthermore, our description enables the calculation of power spectral densities, paving the way for a more thorough investigation of the unexplained "excess noise" in long diffusive junctions and TES reported in recent experiments.