Effect of van der Waals forces on the stacking of coronenes encapsulated in a single-wall carbon nanotube and many-body excitation spectrum

We investigate the geometry, stability, electronic structure and optical properties of C24H12 coronenes encapsulated in a single-wall (19,0) carbon nanotube. By an adequate combination of advanced electronic-structure techniques, involving weak and van der Waals interaction, as well as many-body effects for establishing electronic properties and excitations, we have accurately characterized this hybrid carbon nanostructure, which arises as a promising candidate for opto-electronic nanodevices. In particular, we show that the structure of the stacked coronenes inside the nanotube is characterized by a rotation of every coronene with respect to its neighbors through van der Waals interaction, which is of paramount importance in these systems. We also suggest a tentative modification of the system for this particular rotation to be observed experimentally. A comparison between the calculated many-body excitation spectrum of the systems involved reveals a pronounced optical red-shift with respect to the coronene-stacking gas-phase. The origin of this red-shift is explained in terms of the confinement of the coronene molecules inside the nanotube, showing an excellent agreement with the available experimental evidence.