Two-dimensional materials offer a unique opportunity to explore superconductivity in the two-dimensional (2D) limit with low disorder. IRG1 creates heterostructures of high-quality monolayers of superconductors encapsulated within insulating boron nitride, which provides protection from external disorder and oxidation. In the past year, the team has made three notable discoveries in this area:
- (Under applied magnetic fields, 2D superconductors become extremely sensitive to radiofrequency (RF) noise. Coupling to RF noise can produce a constant-resistance state that has previously been interpreted as an exotic metal, but is actually due to melting of the lattice of magnetic vortices. This effect disappears when samples are RF shielded by filtering.
- In the monolayer limit, the onset of superconductivity in NbSe2 (a conventional BCS superconductor) is not strongly modified from the bulk. However, a true zero-resistance state is only seen in the limit of zero current, magnetic field, and temperature. This effect can also be understood through motion of vortices.
- In the monolayer, Td-MoTe2 shows superconductivity up to 7.5 K – a 60-fold increase over the bulk – and an unusual response to in-plane magnetic fields due to the tilted spins in the electron pocket. This spin texture effect is only observable in the clean limit – where normal-state mean free path is larger than the superconducting coherence length.