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HL: Fachverband Halbleiterphysik

HL 4: Quantum dots and wires: Optical properties I

HL 4.10: Vortrag

Montag, 12. März 2018, 12:00–12:15, EW 201

Strain-dependent optical spectra of carbon nanotubes — •Christian Wagner¹, Jörg Schuster², and André Schleife³ — ¹Center for Microtechnologies, TU Chemnitz, Germany — ²Fraunhofer Institute ENAS, Chemnitz, Germany — ³Department 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 dependence of the CNT band-gap on strain and chirality, which is well explored. However, there is no quantitative model for the strain dependence of optical transitions — which are subject to strong excitonic effects due to the quasi one-dimensional structure of CNTs.

One approach towards such a model is a parametrized description of the quasiparticle gap as well as the scaling relation of the exciton binding energy in CNTs given by Perebeinos et al [1]. However, the description of screening in the scaling relation is insufficient, since for CNTs, a one-dimensional wave-vector dependent dielectric function є(q) is required instead of an effective-medium dielectric constant є₀.

We improve the approach by Perebeinos et al [1] by relating the screening physics in CNTs to the electronic transitions. The resulting model is fitted to electronic-structure calculations within many-body perturbation theory. This enables us to quantitatively predict the strain dependence of optical transitions for any CNT.

[1] V. Perebeinos et al., Phys. Rev. Lett. 92, 257402 (2004).