Longitudinal Proximity Effects in Superconducting Transition-Edge Sensors

TL;DR

This paper experimentally investigates the longitudinal proximity effects in superconducting transition-edge sensors, revealing how critical current depends on size, temperature, and magnetic field, with implications for their design and understanding.

Contribution

It demonstrates the exponential dependence of critical current on size and temperature, and observes long-range proximity effects and Fraunhofer-like oscillations in TES devices.

Findings

Critical current depends exponentially on side length and temperature.

Proximity effects observed over lengths exceeding 100 micrometers.

Fraunhofer-like oscillations in magnetic field indicate Josephson junction behavior.

Abstract

We have found experimentally that the critical current of a square superconducting transition-edge sensor (TES) depends exponentially upon the side length L and the square root of the temperature T. As a consequence, the effective transition temperature Tc of the TES is current-dependent and at fixed current scales as 1/L^2. We also have found that the critical current can show clear Fraunhofer-like oscillations in an applied magnetic field, similar to those found in Josephson junctions. The observed behavior has a natural theoretical explanation in terms of longitudinal proximity effects if the TES is regarded as a weak link between superconducting leads. We have observed the proximity effect in these devices over extraordinarily long lengths exceeding 100 um.