Close look at iron-based superconductor advances theory

Close look at iron-based superconductor advances theory: Surprisingly, however, when the material is "underdoped" with not quite enough cobalt to create superconductivity, an ordinary electric current moves easily along only one axis of the crystal—call it "lengthwise"—but encounters high resistance moving crosswise. This effect increases with the amount of cobalt doping, and may offer a clue to how superconductivity works.

Scanning tunneling microscope (STM) images of the electronic structure of the material in this underdoped state reveal an array of tiny, elongated groups of electrons in an unusual energy state, aligned with the long axis of the crystal, that act as barriers to electrons moving crosswise.