Seminar By Nicolas Regnault, Ecole Normale Supérieure Paris and CNRS

Title: Some updates about moiré fractional phases

Host: Oskar Vafek

Abstract: The recent experimental observations of fractional Chern insulators in moire systems without an applied magnetic field have finally brought these phases of matter to reality more than 10 years after their prediction. These experiments have also raised several challenging questions but also hopes for even more exotic phases. In this talk, we will address two points. First, we will wonder in which case the time-reversal invariant generalization of a fractional Chern, fractional topological insulators, can also be realized in the moiré platforms. We will consider both twisted bilayer MoTe2 and an idealized Landau level model to extract general principles for engineering such exotic phases. Second, the other platform where fractional Chern insulators have been observed, namely pentalayer rhombohedral graphene, appeared to be more difficult to grasp than MoTe2. We will present large scale numerical simulations providing a nuanced picture for the different scenarios that have been proposed to explain the emergence of these fractional phases.