CARBON nanotubes can be switched from acting like a semiconductor to acting like a metal and back again simply by using a magnetic field. This fulfils a prediction based on one of the most fundamental phenomena in quantum physics that says electrons can “sense” a magnetic field even when they are apparently shielded from it.
Some carbon nanotubes are metals and others are semiconductors. Metals are good conductors because their electrons can easily jump from the highest energy levels they normally occupy to the conduction band. In semiconductors the energy needed to jump this “band gap” is greater, so the…
