Depending on how they are fabricated, carbon nanotubes can be metallic or semiconducting. Now, researchers at the University of Illinois have shown that a coaxial magnetic field can be used to convert them from metallic to semiconducting and vice-versa...and back again. In the May 21 issue of Science, researchers present experimental evidence that a nanotube's electronic structure can be altered in response to a magnetic field. The research team consisted of physics professors Alexey Bezryadin and Paul Goldbart, postdoctoral research associate Smitha Vishveshwara and graduate students Ulas Coskun and Tzu-Chieh Wei. Carbon nanotubes are molecules built of sheets of graphite (a hexagonal lattice of carbon atoms) rolled into long cylinders. The manner in which the sheets are rolled and seamed determines whether the tubes are metallic or semiconducting.
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