Experimental observation of the Wigner cusps in a metallic carbon nanotube*

The Wigner cusp is a phenomenon observed in nuclear physics. The cusp is manifested in condensed matter physics in theoretical calculations of scattering induced by impurities: the impurity scattering is highly enhanced as the energy of charge carriers near the threshold energies for another conduction subbands. Such effects are commonly seen in transport calculations of carbon nanotubes and graphene nanoribbons. Yet, the Wigner cusp has never been observed experimentally in condensed matter systems.

Metallic carbon nanotubes sometime show unusual gate dependent conductance characterized by significant suppression of conductance. Such measurements have been attributed to the contributions from the contacts. We have performed length-dependent resistance measurements on a chiral-angle known metallic nanotube and show that such effect is intrinsic to nanotubes. Our tight-binding, recursive Green’s function simulation show that the suppression was the manifestation of the Wigner cusp induced by substrate-bound charged impurities.