Localization and nonlinear resistance in telescopically extended nanotubes.

We have measured the electrical resistance R between the ends of a multiwall carbon nanotube during telescopic extension of the nanotube. R increases monotonically with extension and is hysteresis free, demonstrating that a telescoping nanotube constitutes a near-ideal nanometer-scale rheostat. The functional form of R is nonlinear and consistent with an exponential form predicted for a one-dimensional localized system, with a characteristic localization length 1000-1500 nm.