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Polyyne electronic and vibrational properties under environmental interactions

Authors/others:Wanko, Marius (University of the Basque Country) Cahangirov, Seymur (University of the Basque Country) Shi, LeiRohringer, PhilipLapin, Zachary J. (Eidgenössische Technische Hochschule Zürich) Novotny, Lukas (Eidgenössische Technische Hochschule Zürich) Ayala, Paola (Yachay Tech University) Pichler, ThomasRubio, Angel (University of the Basque Country)
Abstract:Recently the novel system of linear carbon chains inside double-walled carbon nanotubes has extended the length of sp(1) hybridized carbon chains from 44 to thousands of atoms [Shi et al., Nat. Mater. 15, 634 (2016)]. The optoelectronic properties of these ultralong chains are poorly described by current theoretical models, which are based on short chain experimental data and assume a constant environment. As such, a physical understanding of the system in terms of charge transfer and van der Waals interactions is widely missing. We provide a reference for the intrinsic Raman frequency of polyynes in vacuo and explicitly describe the interactions between polyynes and carbon nanotubes. We find that van der Waals interactions strongly shift this frequency, which has been neither expected nor described for other intramolecular C-C stretching vibrations. As a consequence of charge transfer from the tube to the chain, the Raman response of long chains is qualitatively different from the known phonon dispersion of polymers close to the Gamma point. Based on these findings we show how to correctly interpret the Raman data, considering the nanotube's properties. This is essential for its use as an analytical tool to optimize the growth process for future applications.
Number of pages:6
Date of publication:14.11.2016
Journal title:Physical Review B (Condensed Matter and Materials Physics)
Digital Object Identifier (DOI):http://dx.doi.org/10.1103/PhysRevB.94.195422
Publication Type:Article
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