Condensed Matter Physics Seminar: Dynamically Driven Systems: The case of Graphene

Abstract:

Topological insulators are an exotic family of materials where a bulk gap is bridged by surface states which propagate even in the presence of disorder. In some materials the non-trivial topological properties are crafted with an external driving (e.g. a circularly polarized laser), these new state of matter is known as “Floquet topological insulators”.

In the case of graphene, radiation may create bulk band-gaps transforming the system into a two-dimensional Floquet topological insulator.  I will discuss the formation of band gaps at different energies by the action of circularly polarized laser and then show the emergence of laser-induced chiral edge states bridging the gaps in graphene ribbons.

I will show simulations of the dc conductance and quantum Hall response of a Floquet topological insulator. The dc quantum Hall conductance is not directly linked to topological invariants of the dynamical (Floquet) bands. This shows that there are important differences between the conventional topological insulators and the dynamically driven systems.
 

Seminar Organizer: Prof. Shimshon Barad