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Superfluid stiffness of magic-angle twisted bilayer graphene
Miuko Tanaka1,2, Joel Î-J Wang3, Thao H Dinh4
1Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, MA, USA.
Nature
|February 5, 2025
Summary
Superfluid stiffness in magic-angle twisted bilayer graphene (MATBG) is significantly larger than predicted by conventional theories. This unconventional superconductivity is linked to quantum geometric effects and an anisotropic superconducting gap.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Quantum Mechanics
Background:
- Superconductivity in magic-angle twisted bilayer graphene (MATBG) is a key area in moiré systems research.
- Understanding MATBG superconductivity may offer insights into high-critical-temperature superconductors.
Purpose of the Study:
- Directly measure the superfluid stiffness of superconducting MATBG.
- Investigate the underlying physics of superconductivity in this material.
Main Methods:
- Utilized d.c. transport and microwave circuit quantum electrodynamics.
- Measured superfluid stiffness via kinetic inductance.
Main Results:
- Superfluid stiffness found to be much larger than conventional Fermi liquid theory predictions.
- Results align with quantum geometric effects and theoretical predictions.
- Temperature dependence follows a power law, contradicting isotropic Bardeen-Cooper-Schrieffer (BCS) models.
- Observed anisotropic superconducting gap and quadratic dependence of stiffness on current.
Conclusions:
- MATBG exhibits unconventional superconductivity with an anisotropic gap.
- Findings suggest a link between quantum geometry, superfluid stiffness, and unconventional superconductivity in MATBG.
- The developed d.c.-microwave platform is suitable for studying other thin-film superconductors.
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