Josephson dynamics and Shapiro steps at high transmissions: current bias regime

Area of Science:

• Condensed Matter Physics
• Quantum Electronics
• Superconductivity

Background:

• Josephson dynamics in superconducting nanojunctions are crucial for quantum device applications.
• Understanding dissipation mechanisms is key to controlling superconducting circuit behavior.

Purpose of the Study:

• To investigate Josephson dynamics in highly transparent superconducting nanojunctions at low temperatures and subgap voltages.
• To characterize the impact of intrinsic sub-Ohmic dissipation on junction behavior and Shapiro steps.

Main Methods:

• Theoretical investigation of Josephson dynamics.
• Analysis of current-voltage (I-V) characteristics under microwave irradiation.
• Focus on subgap voltages and temperatures where intrinsic dissipation is sub-Ohmic.

Main Results:

• Identified intrinsic sub-Ohmic dissipation in highly transparent superconducting nanojunctions.
• Observed a linear dependence of average voltage on bias current slightly exceeding the critical current.
• Demonstrated significant influence of sub-Ohmic dissipation on integer Shapiro steps.

Conclusions:

• Intrinsic sub-Ohmic dissipation plays a critical role in the electrical characteristics of superconducting nanojunctions.
• This dissipation mechanism directly impacts the formation and behavior of Shapiro steps.
• Findings are relevant for the design and optimization of superconducting electronic devices.