Collective excitations in ultrathin metasurfaces of self-assembled carbon nanotubes

Thin and ultrathin parallel-aligned single-wall carbon nanotube (SWCN) arrays and films are currently in the process of rapid experimental development[1,2]. Self-assembled quasiperiodic SWCN films are shown experimentally to exhibit extraordinary optoplasmonic properties[1]. Here we study theoretically the intrinsic collective quasiparticle excitations responsible for the in-plane electromagnetic (EM) response of ultrathin plane-parallel homogeneous periodic SWCN arrays and weakly inhomogeneous SWCN films[3]. We show that the real part of their in-plane EM response in the CN alignment direction exhibits a negative refraction (NR) band near a quantum interband transition of the constituent CN. In this direction alone, the film behaves as a hyperbolic metasurface while being a featureless dielectric in the perpendicular direction. We study how one can tune the properties of these highly anisotropic metasurfaces. We show that by decreasing the SWCN diameter one can push their one-dimensional NR band into the visible region and using weakly inhomogeneous multi-type SWCN films broadens its bandwidth. – [1]J.A.Roberts, et al., PR Appl. 14, 044006 (2020); Nano Lett. 19, 3131 (2019); [2]W.Gao, et al., ACS Photon. 6, 1602 (2019); [3]I.V.Bondarev & C.M.Adhikari, PR Appl. 15, 034001 (2021).