Reentrant superconductivity in a naturally occurring Josephson junction array tuned by radio-frequency power

Area of Science:

• Condensed Matter Physics
• Quantum Materials

Background:

• Superconductivity typically vanishes at high temperatures or magnetic fields.
• Reentrant superconductivity, where superconductivity reappears under these conditions, is rare and linked to competing orders.

Purpose of the Study:

• To demonstrate reentrant superconductivity in granular aluminum.
• To investigate the tunability of superconductivity using radio-frequency (RF) power.
• To explore the role of many-body correlations in superconductivity.

Main Methods:

• Utilized granular aluminum as a Josephson junction array.
• Applied radio-frequency power to tune the system's superconducting properties.
• Observed Shapiro steps and quantized voltage characteristics.
• Analyzed the transition between superconducting and insulating states.

Main Results:

• Demonstrated reentrant superconductivity tunable by temperature, magnetic field, and RF power.
• Observed giant Shapiro steps indicative of single Josephson junction behavior.
• Showcased a transition from a coherent superconducting (stiff-phase) to an insulating (phase-fluctuating) state via RF power.
• Identified RF power's role in modulating Josephson coupling energy.
• Observed superconductivity reappearance at elevated temperatures due to charge screening effects.

Conclusions:

• Granular aluminum acts as a tunable quantum simulator for complex condensed matter phenomena.
• The study highlights the interplay between single-junction dynamics and many-body correlations.
• Reentrant superconductivity in this system is influenced by Josephson coupling and charge screening, extending beyond single-junction models.