# Dresden 2014 – wissenschaftliches Programm

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# HL: Fachverband Halbleiterphysik

## HL 93: Frontiers of electronic structure theory - Non-equilibrium phenomena at the nano-scale VI (organized by O)

### HL 93.3: Vortrag

### Donnerstag, 3. April 2014, 11:15–11:30, TRE Ma

**Advanced time-evolution method for optical absorption spectra calculations** — •Tobias Sander and Georg Kresse — Computational Materials Physics, University of Vienna, Sensengasse 8/12, 1090 Vienna, Austria

The Green’s function formalism from many-body perturbation theory
gives access to electronic structure calculation within
the quasiparticle picture, as well as provides for calculating optical
absorption spectra. Within the traditional ansatz [1], a
Bethe-Salpeter like
equation for the polarizability is solved. This requires to
diagonalize an in general non-hermitian and complex matrix (BSE
matrix). Usually, the off-diagonal elements of the BSE matrix are
neglected and this is referred to as Tamm-Dancoff approximation.
The computational effort can be reduced by using
the time-evolution ansatz [2] which avoids the matrix
diagonalization. We present a
method based on the time-evolution algorithm, that finally avoids
storing and diagonalizing the BSE matrix.
This leads to a reduction of the scaling w.r.t the system size N from
N^{5} to N^{3}. Finally, we present first results
for typical systems.

[1] S. Albrecht, L. Reining, R. Del Sole, G. Onida,
PRL 80, 4510 (1998)

W. G. Schmidt, S. Glutsch, P. H. Hahn, F. Bechstedt, PRB 67, 085307 (2003)