SPICE Workshop on Quantum Matter for Quantum Technologies, May 21st - May 23rd 2024
Jeanie Lau
Department of Physics, The Ohio State University, Columbus, OH 43221
In a flat band system, the charge carriers’ energy-momentum relation is very weakly dispersive. The resultant large density of states and the dominance of Coulomb potential energy relative to the kinetic energy favor the formation of strongly correlated electron states, such as ferromagnetism, nematicity, and superconductivity. The advent of two-dimensional (2D) materials and their heterostructures has ushered in a new era for exploring, tuning and engineering of flat band system. Here I will give an introduction and overview of the state-of-art of superconductivity in moiré materials. In the second half of the talk, I will present our recent work in twisted bilayer graphene, which the slow Fermi velocity and the small charge density appear to invalidate conventional BCS equations and present a paradox. The paradox is resolved by our experimental demonstration that the superfluid stiffness is dominated by the quantum geometric contribution. If time allows, I will also discuss our recent observation of correlated insulating states at fractional fillings in large angle twisted bilayer graphene.