Longitudinal proximity effects in superconducting transition-edge sensors

Area of Science:

• Superconducting electronics
• Thin-film sensors
• Quantum phenomena

Background:

• Transition-edge sensors (TES) are crucial for sensitive measurements.
• Understanding critical current behavior is key to optimizing TES performance.
• Superconducting weak links exhibit unique quantum effects.

Purpose of the Study:

• To experimentally investigate the critical current dependence on physical parameters in square thin-film TES.
• To theoretically explain the observed critical current behavior using longitudinal proximity effects.
• To explore the influence of magnetic fields on the critical current.

Main Methods:

• Experimental fabrication and characterization of square thin-film superconducting transition-edge sensors.
• Theoretical modeling based on longitudinal proximity effects in superconducting weak links.
• Measurement of critical current as a function of temperature, side length, and applied magnetic field.

Main Results:

• Critical current shows exponential dependence on sensor side length (L) and square root of temperature (T).
• Effective transition temperature (Tc) is current-dependent and scales with 1/L^2.
• Observed Fraunhofer-like oscillations in critical current with applied magnetic field, characteristic of Josephson junctions.
• Longitudinal proximity effect observed over exceptionally long lengths (up to 290 microm).

Conclusions:

• The critical current in thin-film TES is governed by longitudinal proximity effects.
• TES devices exhibit Josephson junction-like behavior, enabling tunable properties.
• The findings advance the understanding and application of superconducting sensors.