SKM 2023 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 26: Focus Session: Frontiers of Electronic-Structure Theory IV (joint session O/HL)
HL 26.6: Talk
Wednesday, March 29, 2023, 12:15–12:30, TRE Ma
Efficient diagonalization of BSE electron-hole Hamiltonian using group theory — •Jörn Stöhler1,2, Dmitrii Nabok1, Stefan Blügel1, and Christoph Friedrich1 — 1Peter Grünberg Institut and Institute for Advanced Simulation, Forschungszentrum Jülich, Germany — 2RWTH Aachen University, Germany
The Bethe-Salpeter equation (BSE) is the state-of-the-art method for the calculation of optical absorption and electron-energy loss spectra including excitonic effects. We solve the BSE by diagonalizing an effective electron-hole Hamiltonian. Often, a high number of k-points is needed to converge the BSE spectra, which leads to a large size of the Hamiltonian matrix and makes its diagonalization very expensive. In this work [1], we use the full spatial symmetry group to transform the electron-hole product basis into a symmetry-adapted product basis, which brings the Hamiltonian into a block-diagonal form and speeds up the subsequent diagonalization. The basis transformation is sparse and causes little overhead. We provide an implementation of our method in the FLAPW code Spex and demonstrate speedups of 36, 52, 12 for Si, BN, and monolayer MoS2, respectively.
We acknowledge financial support by MaX CoE funded by the EU through H2020-INFRAEDI-2018 (project: GA 824143).
[1] J. Stöhler, C. Friedrich, Unpublished