Recent experiments have demonstrated how a dimerized atomic chain of carbon atoms, so-called carbyne, may be fabricated within the hollow center of a single walled or multiwalled carbon nanotube (CNT) [1, 2]. The optical... [ view full abstract ]
Recent experiments have demonstrated how a dimerized atomic chain of carbon atoms, so-called carbyne, may be fabricated within the hollow center of a single walled or multiwalled carbon nanotube (CNT) [1, 2]. The optical properties of both isolated carbon chain and the various CNT species are dominated completely by excitonic effects, reflecting strongly bound and 1D confined electron-hole pairs [3, 4]. While the combined carbyne/CNT system are expected to show similar trends, we also expect this system to display novel excitonic phenomena, e.g., charge transfer excitons where electron and hole are localized respectively on the CNT and carbyne domains.
In this study we (i) investigate the electronic structure of the semiconducting CNT (8,0)/carbyne system using density-functional theory (DFT) with GW correction on top, (ii) We parametrize the DFT band structure in a nearest-neighbour tight-binding formulation by getting the tight binding parameters from fitting the effective mass to the DFT, and (iii) solve the Bethe-Salpeter equation in a singlet basis constructed from the simplified tight-binding states. We show the effect of band hybridization between carbyne and CNT on the single particle optical response as well as excitonic optical response from Bethe-Salpeter method and calculate the exciton binding energy for different bands.
[1] Xinluo Zhao, et. al., Phys. Rev. Lett. 90, 187401 (2003).
[2] Lei Shi, et. al., Nature Materials 15, 634–639 (2016).
[3] Catalin D. Spataru, et. al., Phys. Rev. Lett. 92, 077402 (2004).
[4] Thomas G. Pedersen, Phys. Rev. B, 69, 075207 (2004).
