Recombination of localized quasiparticles in disordered superconductors

Area of Science:

• Condensed matter physics
• Quantum computing
• Superconducting devices

Background:

• Disordered superconductors offer unique properties for quantum circuits and detectors.
• Quasiparticles, fundamental excitations, limit device performance.
• Microscopic mechanisms of quasiparticle relaxation in disordered superconductors remain unclear.

Purpose of the Study:

• To investigate the microscopic mechanisms of quasiparticle relaxation in disordered superconductors.
• To understand how disorder impacts quasiparticle dynamics.
• To explore potential improvements in superconducting device performance.

Main Methods:

• Fabrication of a disordered β-Ta film patterned as a microwave resonator inductor.
• Measurement of quasiparticle relaxation dynamics in the disordered superconductor.
• Analysis of quasiparticle recombination rates and their dependence on disorder.

Main Results:

• Quasiparticle recombination in disordered β-Ta is governed by phonon scattering time.
• Recombination is faster than in ordered superconductors.
• Disorder-induced localized quasiparticles delocalize via phonon absorption before recombination.

Conclusions:

• The observed faster quasiparticle recombination is a phenomenon inherent to disordered superconductors.
• Understanding this mechanism is key to optimizing superconducting quantum circuits and detectors.
• Phonon scattering and quasiparticle delocalization play critical roles in disordered superconductor dynamics.