Dielectric response of aligned SWCNT films: A theoretical versus experimental study

Finite-thickness films of aligned single-wall carbon nanotubes (SWCNT) are demonstrated to have a tunable negative dielectric response in a wide photon energy range[1]. We explain this theoretically using the Maxwell-Garnett (MG) mixing[2] for the dielectric responses of planar periodic arrays of identical SWCNTs[3]. We start with the calculation of the conductivity of an individual SWCNT using the k.p method[4]. Then we derive a semi-analytical expression for the dielectric tensor of an ultrathin finite-thickness periodically aligned SWCNT array. The dielectric responses of about a dozen of SWCNT arrays with different chiralities and very close diameters are then mixed using the MG method to obtain the dielectric response of the SWCNT film which explains the experimental ellipsometry measurements. We also note that the inhomogeneously broadened interband plasmon resonance overlaps with the broadened exciton resonance, making the exciton-plasmon coupling and associated photon bandgap formation possible in these systems[5]. – [1]J.A.Roberts et al, NL 19, 3131 (2019); [2]V.A.Markel, JOSA A33, 1244 (2016); [3] I.V.Bondarev, Opt.Mater.Expr. 9, 285 (2019); [4]T.Ando, J.Phys.Soc.Jpn.74, 777 (2005); [5]I.V.Bondarev, PRB 85, 035448 (2012).