Nano Lett. (2015)

Ever since the formation of a metallic layer was observed at the interface between the two insulators LaAlO3 and SrTiO3 around a decade ago, oxide interfaces have shown a range of interesting phenomena, including magnetism and superconductivity. Various efforts have been focused on the realization of devices with nanometre dimensions. Most of these efforts are based on modifying, by oxidation for example, the material surrounding a conductive channel. Such methods work well, but are not versatile. Srijit Goswami, Andrea Caviglia and colleagues at the University of Delft have now demonstrated that high-quality devices can be obtained by simply evaporating properly designed metallic gates on the surface of a LaAlO3/SrTiO3 interface.

The researchers first showed that by evaporating a single gate with nanometre dimensions they could control the conductivity of the area of the interface under the gate. They then studied a split gate configuration, in which two narrow gates are placed next to each other leaving a small gap in between. Finally, by measuring the electron conductivity at low temperature (around 50 mK), they were able to induce a superconducting-to-insulating transition, and observed signs of Josephson tunnelling. Although these observations are not that surprising, the demonstration of a technique to fabricate nanodevices with various geometries could become an important tool. For example, it may allow transistors to be developed that can be used for fundamental studies of magnetism and superconductivity at the nanoscale.