Arrays of carbon nanoscrolls as deep-subwavelength magnetic metamaterials

We demonstrate theoretically that an array of carbon nanoscrolls acts as a hyperbolic magnetic metamaterial in the THz regime with genuine subwavelength operation corresponding to wavelength-to-structure ratio of about 200. Due to the low sheet resistance of graphene, the electromagnetic losses in an array of carbon nanoscrolls are almost negligible offering a very sharp magnetic resonance of extreme positive and negative values of the effective magnetic permeability. The latter property leads to superior imaging properties for arrays of carbon nanoscrolls which can operate as magnetic endoscopes in the THz where magnetic materials are scarce. Our optical modelling is supplemented with ab initio density-functional calculations of the self-winding of a single layer of graphene onto a carbon nanotube so as to form a carbon nanoscroll. The latter process is viewed as a means to realize ordered arrays of carbon nanoscrolls in the laboratory based on arrays of aligned carbon nanotubes which are nowadays routinely fabricated.