The new material -- a crystal called a topological
superconductor -- has two electronic identities at once. At very
low temperatures, the interior of the crystal behaves like a
normal superconductor, able to conduct electricity with zero
resistance. At the same time, the surface is metallic, able to
carry a current, albeit with some resistance. This is in direct
contrast to most existing materials that are classified as
electronic states of matter, including metals, insulators and
conventional superconductors, which are consistent in how they
do, or don't, conduct electricity. For example, every single
atom of every single copper wire is able to carry a current,
which dissipates a bit as it travels. Similarly, all the
molecules in normal superconductors conduct electricity without
resistance when the material is placed at the appropriate
temperature. "The known states of electronic matter are
insulators, metals, magnets, semiconductors and superconductors,
and each of them has brought us new technology," said