Superconducting Transistor Promises PC Revolution (http://cacm.acm.org)

Andrea Caviglia and colleagues at the University of Geneva in Switzerland have applied a voltage to a single crystal containing strontium titanate and lanthanum aluminate, which created a superconducting version of a field effect transistor (FET). A year ago, the team grew a single crystal containing the two metal oxides as separate segments, and found a layer of free electrons at the interface of the materials. The electron gas flowed without resistance just above absolute zero. Applying the voltage to the interface enabled the team to switch the superconductivity on and off. The team made the first superconducting transistor by using the lanthanum aluminate side of the crystal as a source-drain channel and the strontium titanate layer as the gate. "With no electric field, there is zero resistance between the source and drain as the device is superconducting," Caviglia says. However, applying an electric field to the strontium titanate shifts the layer of free electrons away from the interface and the lanthanum aluminate stops conducting current. Computers that use a superconducting FET would be "much faster than the gigahertz speeds currently available," Caviglia says.