Voltage Fluctuations in ac Biased Superconducting Transition-Edge Sensors

Area of Science:

• Physics
• Superconductivity
• Sensor Technology

Background:

• Superconducting transition-edge sensors (TESs) are crucial for sensitive measurements.
• Understanding noise sources is vital for optimizing TES performance.
• TESs are often modeled as superconducting weak links.

Purpose of the Study:

• To analyze fundamental noise sources in superconducting transition-edge sensors (TESs).
• To investigate noise behavior as a function of bath temperature, normal resistance, and geometry.
• To explain the origin of excess noise observed in TES detectors.

Main Methods:

• Detailed noise analysis of superconducting transition-edge sensors (TESs).
• AC voltage biasing at MHz frequencies.
• Studying noise in the resistive transition across varying detector parameters and bath temperatures.

Main Results:

• Excess noise in the TES electrical bandwidth is explained by equilibrium Johnson noise of quasiparticles.
• Fluctuations at the Josephson frequency and its harmonics significantly contribute to voltage noise.
• The nonlinear response of the weak link, with a sinusoidal current-phase relation, mediates this contribution.

Conclusions:

• Equilibrium Johnson noise and Josephson frequency fluctuations are primary noise contributors in biased TESs.
• The weak link model accurately describes noise behavior in TES detectors.
• This analysis provides a fundamental understanding for improving TES sensor design and performance.