Zero-field superconducting diode effect in small-twist-angle trilayer graphene
- Publisher:
- Springer Nature
- Publication Type:
- Journal Article
- Citation:
- Nature Physics, 2022, 18, (10), pp. 1221-1227
- Issue Date:
- 2022-10-01
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| Filename | Description | Size | |||
|---|---|---|---|---|---|
| s41567-022-01700-1.pdf | 4.88 MB |
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The critical current of a superconductor can be different for opposite directions of current flow when both time-reversal and inversion symmetry are broken. Such non-reciprocal behaviour creates a superconducting diode and has recently been experimentally demonstrated by breaking these symmetries with an applied magnetic field or by the construction of a magnetic tunnel junction. Here we report an intrinsic superconducting diode effect that is present at zero external magnetic field in mirror-symmetric twisted trilayer graphene. Such non-reciprocal behaviour, with sign that can be reversed through training with an out-of-plane magnetic field, provides direct evidence of the microscopic coexistence between superconductivity and time-reversal symmetry breaking. In addition to the magnetic-field trainability, we show that the zero-field diode effect can be controlled by varying the carrier density or twist angle. A natural interpretation for the origin of the intrinsic diode effect is an imbalance in the valley occupation of the underlying Fermi surface, which probably leads to finite-momentum Cooper pairing and nematicity in the superconducting phase.
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