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Updated: Feb 8, 2026
11:42
Fabrication of Gate-tunable Graphene Devices for Scanning Tunneling Microscopy Studies with Coulomb Impurities
Published on: July 24, 2015
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Gate-Tunable Josephson Diodes in Magic-Angle Twisted Bilayer Graphene.
Alexander Rothstein1,2, Robin Joey Dolleman1, Lennart Klebl3,4
1JARA-FIT and 2nd Institute of Physics, RWTH Aachen University, 52074 Aachen, Germany.
Nano Letters
|February 6, 2026
Summary
Researchers observed a tunable Josephson diode effect in magic-angle twisted bilayer graphene (MATBG) Josephson junctions (JJs). Gate voltage controls the diode
Area of Science:
- Condensed Matter Physics
- Quantum Materials
- Superconductivity
Background:
- Magic-angle twisted bilayer graphene (MATBG) exhibits unique electronic properties due to moiré superlattices.
- Josephson junctions (JJs) are fundamental building blocks in superconducting electronics and quantum circuits.
- The Josephson diode effect, a non-reciprocal current flow in JJs, is crucial for device applications.
Purpose of the Study:
- To investigate the Josephson diode effect in gate-defined JJs within MATBG.
- To understand the role of kinetic inductance and supercurrent distribution in the observed diode behavior.
- To explore the tunability and polarity control of the Josephson diode effect via gate voltage.
Main Methods:
- Low-temperature measurements of adjacent, gate-defined Josephson junctions in MATBG.
- Characterization of Josephson current interference patterns.
- Analysis of gate-voltage dependence of the Josephson diode effect.
Main Results:
- Both JJs exhibited a prominent, gate-tunable Josephson diode effect near a moiré filling factor of ν = -2.
- The diode behavior was attributed to large kinetic inductance and non-uniform supercurrent distribution.
- Microscopic inhomogeneities, like twist angle variations, influenced individual JJ behavior and diode characteristics.
- Gate voltage allowed tuning of diode efficiency and reversal of polarity at fixed magnetic fields.
Conclusions:
- The study demonstrates gate-tunable Josephson diode effects in MATBG JJs.
- Non-uniform supercurrent distribution, influenced by material inhomogeneities, is key to the diode behavior.
- Findings provide pathways for engineering Josephson diode performance in superconducting quantum circuits.
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