Accurate models of 2D materials and heterostructures: balancing between reciprocal- and real-space descriptions

For more than a century, the notion of band structure remained the most important instrument for studying crystalline solids in the physics community. At the same time, an even older picture of chemical bonding, usually considered at an empirical level, continues serving the chemistry community. The Wannier function formalism provides a rigorous connection between these two complementary points of view. In my seminar, I would like to show a number of examples of applying this formalism to understanding and accurate modelling of two-dimensional materials and moiré heterostructures. I will first explain how the intrinsic gauge freedom of Wannier functions can be exploited for explaining the structural and chemical trends [1] across the entire family of transition metal dichalcogenides [2] as well as the tendency towards forming charge-density-wave and distorted phases in these materials [3]. The second part of my seminar is dedicated to constructing tight-binding Hamiltonians for accurate modelling of moiré heterostructures. I will take twisted double bilayer graphene as a starting point [4-6] and present our recent results on related graphene systems modelled using large-scale tight-binding model calculations [7-11].

Speaker: Oleg Yazyev, Ecole Polytechnique Federale de Lausanne