# Dresden 2017 – wissenschaftliches Programm

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# HL: Fachverband Halbleiterphysik

## HL 73: Electronic-Structure Theory: New Concepts and Developments in Density Functional Theory and Beyond - VI

### HL 73.7: Vortrag

### Donnerstag, 23. März 2017, 12:00–12:15, GER 38

**Ab initio calculations and strain-dependent scaling of excitons in carbon nanotubes** — •Christian Wagner^{1,3}, Jörg Schuster^{2}, Michael Schreiber^{3}, and André Schleife^{4} — ^{1}Center for Microtechnologies, TU Chemnitz, Germany — ^{2}Fraunhofer Institute ENAS, Chemnitz, Germany — ^{3}Institute of Physics, TU Chemnitz, Germany — ^{4}Department for Materials Science, UIUC, USA

Optical transitions in carbon nanotubes (CNTs) show a strong strain sensitivity, which makes them suitable for optical strain sensing at the nano-scale and for strain-tunable emitters. The origin of this effect is the band-gap change, depending on strain and chirality, which is well explored. However, there is no quantitative model for the strain dependence of optical transitions — as they are subject to strong excitonic effects due to the quasi one-dimensional structure of CNTs.

One approach towards such a model is the scaling relation of CNT excitons with respect to dielectric constant, reduced mass, and CNT radius given by Perebeinos *et al*.
However, the description of screening in this model is insufficient, since for CNTs, a one-dimensional wave-vector dependent dielectric function є(*q*) is needed instead of an effective-medium dielectric constant є_{0}.

We achieve this by combining the scaling relation with the wave-vector dependent screening model by Deslippe *et al*.
The strain-dependent scaling is fitted to electronic-structure calculations within many-body perturbation theory as a reference.
This enables us to quantitatively predict the strain dependence of optical transitions for any CNT.