Superconductivity in single-layer NbSe2
Kin Fai Mak, Pennsylvania State University
The discovery of graphene has stimulated not only the field of carbon nanoelectronics, but also studies of novel electronic phenomena in a wide range of atomically thin van der Waals’ materials. In this talk, I will discuss our recent effort in the isolation of a single layer of niobium diselenide (NbSe2), a new non-centrosymmetric superconductor. As a result of the crystal symmetry and the strong spin-orbit interactions, the electron spin in single-layer NbSe2 becomes Ising-like (i.e. spins locked to the out-of-plane direction), giving rise to unique magnetic properties in the superconducting state. I will present measurements of the material’s upper critical field, which significantly exceeds the conventional Pauli paramagnetic limit, supporting the Ising pairing mechanism. I will also discuss our measurements of the superconducting gap by tunneling spectroscopy that further provide evidence for finite spin susceptibility arisen from the mixed parity pairing correlations. Our studies pave the way for the search for topological superconductivity in two-dimensional materials.