Berlin 2015 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 74: Frontiers of electronic structure theory: 2D TMDC and excitonic effects

HL 74.10: Talk

Thursday, March 19, 2015, 13:00–13:15, MA 004

Optical excitations in MoS₂ within ab-initio many-body perturbation theory — •Matthias Drüppel, Peter Krüger, and Michael Rohlfing — Institut für Festkörpertheorie, Westfälische Wilhelms-Universität, 48149 Münster, Germany

The transition metal dichalcogenides (TMDC), and MoS₂ as its most prominent member, open the door to a field of two dimensional atomically thin semiconductors which offer rich physics.

The state of the art theoretical description of electronic excitations in these materials starts with density-functional calculations (DFT), followed by the GW method in combination with a solution of the Bethe-Salpeter equation. The converged calculation (especially with respect to the size of the basis, i.e. number of plane waves, and k-meshs) of the last two steps has shown to be numerically extremely challenging.

We apply the efficient LDA+GdW [1] approach to the excited states which enables us to describe electronic excitations in MoS₂ at substantially lower numerical cost. In the LDA+GdW approximation the quasiparticle self-energy corrections to the LDA-DFT energies result from the difference between the correct screening (semiconducting) and hypothetical metallic screening.

This approach sets us in a position where more atoms per unit cells can be treated, e.g., for defects and for MoS₂ on substrates.

[1] M. Rohlfing, Phys. Rev. B. 82, 205127 (2010)