Excitonic fine structure in emission of linear carbon chains

Exciton energy spectra in polyyne chains

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Recently, we have experimentally observed signatures of sharp exciton peaks in the photoluminescence spectra of bundles of monoatomic carbon chains stabilized by gold nanoparticles and deposited on a glass substrate [1]. Here, we estimate the characteristic energies of excitonic transitions in this complex quasi-one-dimensional nano-system with use of the variational method.

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“…Introduction.-Being monoatomic chains of carbon atoms carbynes represent ultimate one-dimensional crystals. Carbynes are linear chains of sp 1 -hybridized carbon atoms. Their two known allotropes are polyyne, characterized by alternating single and triple electronic bonds between carbon atoms, and cumulene, characterized by double bonds between atoms.…”

“…In order to predict the quantum efficiency of carbon-based optical nano-emitters one should learn more about excitons in linear carbon chains. The exciton binding energy in sp 1 carbon may be quite large due to the strong two-dimensional quantum confinement. Recently, we detected the strong excitonic features in low-temperature photoluminescence spectra of polyyne bundles stabilized by gold nano-particles and deposited on a glass substrate.…”

“…The focus of our study was on elongated polyynic molecules, containing straight parts of even numbers of atoms (from 8 to 24) regularly separated with kinks. The synthesised sp 1 -hybridization chains were packed in hexagon bundles characterised by the distance between neighboring parallel chains of 5.35 A [6]. The chains were hold together by the Van der Waals force (see the schematic in Fig.…”

“…1(b,c)). The triplet is invariably composed of a sharp intense peak accompanied by two broader satellites shifted by about 15 and 40 meV [1] to the lower energy side of the main peak, respectively. Very interestingly, the triplet structure is found to be nearly identical in carbon chains of different lengths.…”