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Momentum space AC Josephson effect and intervalley coherence in multilayer graphene
1Department of Physics and Astronomy, University of Kentucky, Lexington, KY, USA.
Nature Communications
|December 24, 2025
Summary
We discovered phase-coherent electron transport in rhombohedral multilayer graphene, analogous to the Josephson effect in superconductors. This phenomenon, driven by a magnetic field, generates an AC Hall response, serving as a signature of the intervalley-coherent state.
Area of Science:
- Condensed matter physics
- Quantum mechanics
- Materials science
Background:
- Electron transport phenomena like superconductivity and charge-density waves rely on quantum phase coherence.
- Rhombohedral multilayer graphene exhibits an intervalley-coherent (IVC) state, but its transport dynamics are not fully understood.
Purpose of the Study:
- To identify and characterize phase-coherent electron dynamics within the IVC state of rhombohedral multilayer graphene.
- To explore the potential for novel electronic transport phenomena analogous to superconductivity.
Main Methods:
- Microscopic calculations of phase-number free-energy parameters.
- Theoretical modeling of electron transport under static magnetic fields.
- Analysis of oscillating intervalley currents and orbital magnetization.
Main Results:
- A static magnetic field induces an oscillating intervalley current in the IVC state.
- This oscillating current generates an oscillating orbital magnetization.
- A detectable AC Hall response is produced, analogous to the AC Josephson effect.
Conclusions:
- The observed AC Hall response is an experimental signature of the intervalley-coherent order in rhombohedral multilayer graphene.
- This work establishes a momentum-space analog of the Josephson effect.
- The findings highlight potential technological applications of phase-coherent transport in graphene systems.
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