Large Tunable Kinetic Inductance in a Twisted Graphene Superconductor

Area of Science:

• Condensed matter physics
• Materials science
• Quantum electronics

Background:

• Twisted graphene moiré heterostructures exhibit flat bands at magic angles, leading to strong electron interactions and emergent phenomena like superconductivity.
• These superconducting phases are electrostatically tunable, making them promising for novel electronic devices.

Purpose of the Study:

• To investigate superconductivity in twisted trilayer graphene.
• To characterize the kinetic inductance and critical current density of these intrinsic superconductors.
• To explore the relationship between kinetic inductance, critical current density, and superconducting coherence length.

Main Methods:

• Fabrication of twisted trilayer graphene.
• Integration of twisted trilayer graphene as a weak link in a superconducting quantum interference device (SQUID).
• Measurement of the current phase relation to determine kinetic inductance and critical current density.

Main Results:

• Demonstrated large and tunable kinetic inductance (up to 150 nH/sq) in both electron and hole-type twisted trilayer graphene superconductors.
• Established a universal relationship between kinetic inductance, critical current density, and superconducting coherence length.
• Extracted an upper bound of approximately 200 nm for the superconducting coherence length.

Conclusions:

• Twisted trilayer graphene hosts robust intrinsic superconductivity with significant kinetic inductance.
• The large coherence length in these materials has important implications for understanding and utilizing their superconducting properties.
• These findings pave the way for applications in tunable superconducting devices and quantum electronics.