Theory of High-Field Transports in Metallic Single-Wall Nanotubes

TL;DR

This paper proposes a new interpretation for high-field transport behaviors in metallic single-wall carbon nanotubes, suggesting supercurrent flow within the wall and normal currents outside, explaining the observed non-Ohmic to Ohmic transition.

Contribution

It introduces a novel interpretation involving supercurrent and normal currents to explain high-bias transport phenomena in metallic nanotubes, contrasting with ballistic electron models.

Findings

Supercurrent flows in the nanotube wall below 150K.

High bias destroys supercurrent, leading to Ohmic behavior.

Temperature dependence of the zero-bias anomaly is explained.

Abstract

Individual metallic single-wall carbon nanotubes show unsual non-Ohmic transport behaviors at high bias fields. For low resistance contact samples, the differential conductance dI/dV increases with increasing bias, reaching a maximum at $\sim$ 100mV. As the bias increases further, dI/dV drops dramatically [Yao et al., Phys. Rev. Lett. 84, 2941 (2000)]. The higher the bias, the system behaves in a more normal (Ohmic) manner. This so-called zero-bias anomaly is temperature-dependent (50--150K). We propose a new interpretation. Supercurrent runs in the graphene wall below $\sim$ 150K. The normal conduction-electron currents run outside the wall, which are subject to the scattering by phonons and impurities. The currents along the tube induce circulating magnetic fields and eventually destroy the supercurrent in the wall at high enough bias, and restore the Ohmic behavior. If the prevalent ballistic electron model is adopted, then the scattering effects cannot be discussed.