Zero Crossing Steps and Anomalous Shapiro Maps in Graphene Josephson Junctions

Area of Science:

• Condensed Matter Physics
• Quantum Phenomena

Background:

• The AC Josephson effect produces Shapiro steps (quantized voltage) in Josephson junctions under RF radiation.
• This effect is a key example of driven-dissipative quantum phenomena and is used in voltage standards.
• Shapiro steps are crucial for characterizing novel junction materials.

Purpose of the Study:

• To investigate Shapiro steps in a tunable graphene-based Josephson junction.
• To explore how various parameters influence Shapiro step patterns.
• To compare observed behaviors with the conventional Resistively and Capacitively Shunted Junction (RCSJ) model.

Main Methods:

• Studied Shapiro steps in a graphene Josephson junction with tunable parameters.
• Varied carrier density, temperature, RF frequency, and magnetic field.
• Simulated junction behaviors to understand observed trends.

Main Results:

• Observed diverse Shapiro step patterns by altering system parameters.
• Identified key differences between graphene junction behavior and the conventional RCSJ model.
• Demonstrated straightforward simulation of observed behaviors.

Conclusions:

• The study provides a comprehensive understanding of Shapiro steps in graphene Josephson junctions.
• Findings can aid in interpreting measurements in more complex quantum materials.
• Highlights the utility of graphene junctions for exploring driven-dissipative quantum effects.