Superconductivity
Does a twisted MoTe2 bilayer superconduct in an unusual way?
Open access · cc by · source: Europe PMC
Short junctions of twisted bilayer MoTe2 carried supercurrent that survived higher fields and temperatures than the superconducting contacts and was weakest at zero magnetic field, unlike an untwisted control.
Study at a glance
- Design
- Other — Low-temperature transport and electron-microscopy experiment on Pd7MoTe2/twisted-MoTe2/Pd7MoTe2 junctions, with a natural-bilayer junction as a control
- N
- A handful of devices: twisted-bilayer transport devices D2 and D3, natural-bilayer device D4, a monolayer comparison device, and separate TEM samples
- Population
- Twisted (about 3.7°) and natural bilayer MoTe2 junctions about 100 nm long between superconducting Pd7MoTe2 pads
- Outcome
- Resistance versus temperature, critical current versus magnetic field, critical field, and normal-state resistance
Structured fields used in claim comparison tables when every cited study has a complete layer.
Key findings
Resistance dropped to zero just below about 1 K and the twisted junction had a critical current of about 42 nA. Superconducting fluctuations in the twisted junction persisted to about 1.2–1.3 K and to fields near 2.2 T, while the Pd7MoTe2 pads lost superconductivity above about 1.2 T. Instead of the usual peak at zero field, the junction's critical current showed a V-shaped minimum at zero field, reproducible across devices and gate voltages. In the natural bilayer control, both anomalies disappeared, pointing to the missing inversion symmetry of the twisted lattice.
Methodology
The authors grew a superconducting compound, Pd7MoTe2, into encapsulated MoTe2 bilayers by gentle annealing, leaving a narrow junction of MoTe2 (about 100 nm) between two superconducting pads. They confirmed with atomic-resolution electron microscopy that the interface was sharp and the moiré pattern intact. They then measured resistance and critical current versus temperature and perpendicular magnetic field down to millikelvin temperatures, comparing twisted bilayers with an inversion-symmetric natural bilayer made the same way.
Limitations
The pairing mechanism is not established: the mix of even- and odd-parity pairing is the authors' speculation, not a measurement. The metallic normal-state conduction of these short junctions (MoTe2 should be insulating) is unexplained. Only a few devices were measured, at a single twist angle, and the hoped-for link to fractional Chern insulator states is not yet shown.
How this study connects
Role on claims
Each row is a claim on a concept or method page where this paper supports, challenges, or qualifies the statement. Roles are hand-checked — not a model guess.
Broken symmetry and thinness produce behaviour ordinary superconductors lack.
Two-dimensional superconductors can exceed the usual Pauli paramagnetic limit for in-plane fields: printed 1T'-WS2 monolayer films had an extrapolated in-plane critical field of about 30 T against a 13.1 T Pauli limit, and twisted MoTe2 junctions showed critical currents with a V-shaped minimum at zero field that vanished in untwisted controls.
Evidence for the claim as stated.
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