Berlin 2018 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 54: Organic semiconductors
HL 54.3: Vortrag
Freitag, 16. März 2018, 10:00–10:15, EW 203
Core-Level Excitations in Oligothiophene Crystals from Ab-Initio Many-Body Theory — •Konstantin Lion, Caterina Cocchi, and Claudia Draxl — Physics Department and IRIS Adlershof, Humboldt-Universität zu Berlin D-12489 Berlin
We study core-level excitations in a series of linear crystalline oligothiophenes, i.e., bithiophene, quaterthiophene, and sexithiophene. Employing the full-potential all-electron exciting code [1], we compute X-ray absorption spectra from first principles through the solution of the Bethe-Salpeter equation, with a fully relativistic treatment of core states [2]. We investigate transitions from the carbon K, the sulfur K, and the sulfur L2,3 edges. Our results, in very good agreement with available experimental data [3, 4], reveal the excitonic character of the near-edge resonances and allow us to resolve the individual contributions from inequivalent atoms. Core-level excitations in these systems exhibit strong excitonic effects, with electron-hole binding energies ranging from 3 to 2 eV, going from bithiophene to sexithiophene. Only in the spectrum from the carbon K edge, the individual contributions from inequivalent atoms show distinct features. Peaks in this spectrum are attributed to transitions from two types of carbon atoms, either sharing a covalent bond to a sulfur atom or not.
. . [1] A. Gulans et al., J. Phys.: Condens. Matter 26, 363202 (2014).
[2] C. Vorwerk et al., Phys. Rev. B 26, 155121 (2017).
[3] P. Väterlein et al., Surf. Sci. 452, 20 (2000).
[4] U. Hörmann et al., J. Phys. Chem. C 118, 26462 (2014).