Speaker: Adarsh Patri, UBC.

Time: 10:00-11:00am

Location: BRIM 311

Title: Quantum Anomalous Hall Effects in Rhombohedral Graphene Moiré Structures 

Abstract: A recent series of experiments in two-dimensional moiré materials have discovered the physics of quantum Hall effect in the absence of an external magnetic field. These so-called “(Integer/Fractional) Quantum Anomalous Hall” phases have been observed in twisted transition metal dichalcogenide MoTe2 moiré heterostructure, as well as more recently in pentalayer rhombohedral graphene aligned with a hexagonal Boron-Nitride (hBN) substrate. Unlike the standard theoretical framework of the quantum Hall effect, where one has a flat band at the single-particle level, these discoveries provide a fertile ground for exploring the minimal conditions that are required to realize and stabilize such exotic phases of matter. In this talk, I will examine the microscopic origin of both the integer and fractional QAH phases in N-layer graphene aligned with hBN through a combination of Hartree-Fock methods and Exact Diagonalization. I will also discuss the delicate role of the moiré superlattice potential in determining the ultimate ground state in strongly-correlated two-dimensional moiré materials. Time-permitting, I will also briefly touch on the phenomenology of the recently observed extended quantum anomalous Hall effect in pentalayer graphene aligned with hBN.

Bio: Adarsh completed his undergraduate degree at the University of Waterloo, and his PhD at the University of Toronto under the supervision of Yong-Baek Kim in 2021. He was a postdoctoral research associate from 2021—2024 at the Massachusetts Institute of Technology working with Senthil Todadri.