Evidence for two time scales in long SNS junctions.

Area of Science:

• Condensed Matter Physics
• Superconductivity
• Mesoscopic Physics

Background:

• Superconductor-normal metal-superconductor (SNS) Josephson junctions are crucial in quantum electronics.
• Understanding the dynamics of these junctions under external stimuli is vital for device applications.
• Previous studies have explored various aspects of SNS junction behavior, but a clear distinction of current-limiting mechanisms under microwave excitation remained elusive.

Purpose of the Study:

• To investigate the dynamic behavior of long SNS Josephson junctions under microwave excitation.
• To differentiate the physical mechanisms controlling critical and retrapping currents.
• To establish the relationship between excitation frequency and scattering processes within the junction.

Main Methods:

• Utilizing microwave excitation across a broad frequency range (10 MHz–40 GHz).
• Measuring dc voltage versus dc current characteristics to determine critical and retrapping currents.
• Analyzing the dependence of these currents on excitation frequency and relating them to characteristic timescales.

Main Results:

• Identified two distinct timescales influencing critical and retrapping currents.
• Observed that critical current increases when excitation frequency exceeds the inverse diffusion time (elastic scattering).
• Found that retrapping current is significantly modified when excitation frequency surpasses the electron-phonon rate (inelastic scattering).

Conclusions:

• Critical and retrapping currents in long SNS Josephson junctions are governed by different dynamic processes.
• Elastic scattering, related to diffusion time, dictates the critical current.
• Inelastic scattering, linked to electron-phonon interactions, influences the retrapping current.