Description:

Dr. Leo Li, Columbia University

Title: Graphene Double-layers: Exciton condensate and beyond

Abstract: A graphene double layer heterostructure is achieved by bringing two monolayer graphene in close vicinity, separated by an insulating hexagonal boron nitride (hBN) crystal that is ~2nm thick. The strong interlayer Coulomb coupling makes such structure an ideal platform to study 2-component ground states in the quantum Hall effect regime, including, but not limited to, exciton condensate. In this talk, I will present results from graphene double layer in corbino geometry, where transport measurements directly probe bulk ground state without interference of edge channels. The combination of parallel flow and counterflow measurements offer insights into the pairing mechanism and ground state order of the exciton condensate. Additionally, access to magnetic field up to 31T lead to the first experimental observation of an interlayer coherent fermi sea at ⅓ filling in each layer and its associated 2-component fractional quantum Hall sequence. I will explore the 2-dimensional phase space of graphene double layer, and the intricate landscape of novel states of matter such as exciton superfluid at fractional filling.

Host: Bill Halperin