Unconventional superconductivity in two-dimensional Van der Waals materials
Miguel M. Ugeda
Donostia International Physics Center (DIPC), Paseo Manuel de Lardizábal 4, 20018 San Sebastián, Spain.
Centro de Física de Materiales (CSIC-UPV-EHU), Paseo Manuel de Lardizábal 5, 20018 San Sebastián, Spain.
Ikerbasque, Basque Foundation for Science, 48013 Bilbao, Spain.
Van der Waals materials provide an ideal platform to explore superconductivity in the presence of strong electronic correlations, which are detrimental of the conventional phonon-mediated Cooper pairing in the BCS-Eliashberg theory and, simultaneously, promote magnetic fluctuations. Despite recent progress in understanding superconductivity in layered materials, the glue pairing mechanism remains largely unexplored in the single-layer limit, where electron-electron interactions are dramatically enhanced. In this talk, I will present experimental evidence of unconventional Cooper pairing mediated by magnetic excitations in monolayers of Se-based transition metal superconductors (NbSe2 and TaSe2), two model strongly correlated 2D materials.
2D TMD materials will reduce the enormous complexity associated with the investigation of unconventional superconductivity, and will rapidly allow us to expand our current limited knowledge of non-phononic Cooper pairing. They offer unprecedented simplicity for modelling as compared to the most studied bulky unconventional superconductors, i.e., cuprates, Fe-pnictides and heavy-fermion compounds. In two dimensions, TMD superconductors are even simpler to model than twisted bilayer graphene, where superconductivity is intrinsically linked to specific magic angles. From the experimental point of view, our work opens the tantalizing possibility to explore unconventional superconductivity in simple, scalable and widely accessible 2D materials.