Dresden 2017 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 88: Electronic Structure Theory: New Concepts and Developments in Density Functional Theory and Beyond - VI

O 88.7: Vortrag

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

Ab initio calculations and strain-dependent scaling of excitons in carbon nanotubes — •Christian Wagner1,3, Jörg Schuster2, Michael Schreiber3, and André Schleife41Center for Microtechnologies, TU Chemnitz, Germany — 2Fraunhofer Institute ENAS, Chemnitz, Germany — 3Institute of Physics, TU Chemnitz, Germany — 4Department 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 є0.

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.

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