Superconductivity, Strong Correlations, and Flat Electronic Bands in (un)-Twisted Graphene Multilayers
Prof. Stevan Nadj-Perge
Professor of Applied Physics and Materials Science
Caltech
When two graphene sheets are rotationally misaligned (i.e., twisted) by approximately one degree and stacked together, the resulting bilayer exhibits various correlated, superconducting, and topological electronic phases. The origin of these distinctive phases, emerging at this particular twist angle, can be traced back to the weakly dispersive ('flat') electronic bands in which the kinetic energy of electrons is heavily suppressed, and interactions between electrons dominate. In this talk, I will discuss several experiments providing insights into the electronic phases and band structure of twisted bilayer graphene obtained using scanning tunneling microscopy and cryogenic transport measurements. Then, I will overview several other graphene-based correlated and superconducting systems, highlighting their striking similarities and differences. Besides bilayers, we will discuss signatures of strong correlations and unconventional superconductivity in twisted tri-, quadri-, and penta-layers, and compare these findings to measurements of untwisted graphene bilayers that can exhibit similar phenomenology in strong displacement fields. Finally, I will share thoughts on future opportunities in this research field and the potential of these materials for quantum science applications.
Hosted by Prof. Forró