Title: Excitons in 2D Materials and van der Waals Heterostructures
When: Thursday, March 23, 2024, 12:00
Place: Department of Condensed Matter Physics, Faculty of Sciences, Module 3, Seminar Room (5th Floor)
Speaker: Maurício F. C. Martins Quintela, University of Minho, Portugal.
In this talk, I will provide a brief overview of the work developed during my PhD following the same logical order present in the defense of the dissertation. First, I will outline a pair of simple variational method for computing the dynamical polarizability of Wannier excitons in layered materials. Afterwards, a simple approach to the Bethe-Salpeter equation will be introduced, allowing for semi-analytical computation of excitons in monolayer materials, fol- lowed by its extension to multilayer systems. Excitons in rhombohedral trilayer graphene are of particular interest for multilayer systems due to the tunability of the system’s bandgap via an external gate voltage. Having computed the excitonic states, the method for obtaining the conductivity tensor components is discussed with specific emphasis on both optical selection rules and on the inclusion of continuum states. The effect of additional hopping terms, together with the tunability of the optical response in the trilayer are also analyzed before turning to the computation of the SHG non–linear optical response. Finally, the lattice structure is deformed in the out–of–plane direction, leading to emergent out–of–plane linear and non–linear responses with new observable selection rules.
