Strongly correlated excitonic insulator in Coulomb-coupled bilayers
Max Planck Lecture on Non-Equilibrium Quantum Phenomena
- Date: Jun 30, 2021
- Time: 03:00 PM - 04:00 PM (Local Time Germany)
- Speaker: Kin Fai Mak
- Cornell University
- Location: online via Zoom
- Host: Andrea Cavalleri, Angel Rubio
Excitonic insulators (EIs) arise from the formation of bound electron-hole pairs (excitons) in semiconductors and provide a solid-state platform for quantum many-boson physics. Strong exciton-exciton repulsion is expected to stabilize condensed superfluid and crystalline phases by suppressing both density and phase fluctuations. Although spectroscopic signatures of EIs have been reported, conclusive evidence for strongly correlated EI states has remained elusive.
In this talk, I will discuss the realization of strongly correlated EIs in Coulomb-coupled bilayers of 2D semiconductors. In particular, I will present direct thermodynamic evidence of the EI ground state and discuss the exciton phase diagram that reveals both the Mott transition and interaction-enhanced quasi-condensation. If time permits, I will also discuss the realization of a strongly correlated EI in a moiré lattice, effectively realizing the Bose-Hubbard model in a solid-state platform.
I received my PhD in physics from Columbia University working with Prof. Tony Heinz on optical spectroscopy of 2D materials such as graphene and MoS2. As a postdoc, I worked with Prof. Paul McEuen and Prof. Jiwoong Park at Cornell on the optoelectronic properties of 2D semiconductors. I started my faculty position at Penn State University in 2014 and moved back to Cornell in 2018. I am now an associate professor of physics and of applied and engineering physics. My current research interests include magnetism, superconductivity, strong correlation physics and exciton physics in 2D materials and their heterostructures.