Nonequilibrium Quasiparticle Dynamics in a MoRe-Based Superconducting Resonator under IR Excitation

TL;DR

This study investigates how pulsed infrared light affects a MoRe superconducting resonator near 5 K, revealing nonequilibrium quasiparticle dynamics that influence device response and potential detector applications.

Contribution

It provides new insights into nonequilibrium quasiparticle behavior in MoRe superconductors under IR excitation, highlighting nonlinear responses and steady-state regimes.

Findings

Infrared pulses cause resonance distortions and frequency shifts due to quasiparticle generation.

Dissipation saturates at high powers, indicating a quasiparticle relaxation bottleneck.

Results suggest potential for MoRe in microwave kinetic-inductance detectors.

Abstract

The response of a MoRe-based superconducting resonator operating near 5 K to pulsed infrared irradiation is investigated, and the underlying physical mechanisms are analyzed. The device exhibits a pronounced nonlinear response dominated by nonequilibrium quasiparticle dynamics rather than uniform thermal heating. Infrared pulses produce strong distortions of the resonance curve and a transient decrease in the resonance frequency, consistent with increased kinetic inductance caused by quasiparticle generation. The frequency shift scales approximately linearly with absorbed power, whereas the dissipation response saturates at higher powers, indicating the formation of a nonequilibrium steady-state quasiparticle population. These observations demonstrate a transition from a linear pair-breaking regime to a saturated dissipation regime, likely associated with a quasiparticle relaxation bottleneck or partial suppression of the smaller superconducting gap in MoRe. The results highlight the relevance of nonequilibrium processes in MoRe and confirm its potential for microwave kinetic-inductance detector applications.