Abstract
When atomically thin two-dimensional materials are layered, they often form incommensurate noncrystalline structures that exhibit long-period moire patterns when examined by scanning probes. In this talk I present a methodology that uses information obtained from ab initio calculations performed on short-period crystalline structures to derive effective Hamiltonians that are able to efficiently describe the influence of the moire pattern superlattices on electronic properties. We applied our approach to obtain the Hamiltonian of graphene on hexagonal boron nitride (G/BN) that can be used to calculate electronic properties of interest for arbitrary twist angles and lattice constants. We show that our multiscale approach can be used to obtain electronic structure models that have predictive accuracy, and that moire strains can play an important role in reconfiguring the mechanical and electronic properties of G/BN such as its band gap. The bridge between the continuum and the lattice Hamiltonian established by our theory can be used in realistic simulations of G/BN subject to disorder or perpendicular magnetic fields.
References:
[1] J. Jung, A. Raoux, Z.H. Qiao and A. H. MacDonald, ‘Ab-Initio Theory of Moiré Superlattice Bands in Layered Two-Dimensional Materials’, Physical Review B 89, 205414 (2014). [2] J. Jung, A. DaSilva, A. H. MacDonald, and S. Adam, ‘Origin of band gaps in graphene on hexagonal boron nitride’, Nature Communications 6:6308 (2015). [3] N. Leconte, A. Ferreira, and J. Jung, ‘Efficient multiscale lattice simulations of strained and disordered graphene’, Chapter 2 of 'Semiconductors and semimetals, 2D materials’, Elsevier 2016.
Coffee and tea will be served 20 minutes prior to the seminar.
Anyone interested is welcome to attend.