Electrostatic control of the evolution from a superconducting phase to an insulating phase in ultrathin YBa₂Cu₃O(7-x) films.

The electrical transport properties of ultrathin YBa₂Cu₃O(7-x) films have been modified using an electric double layer transistor configuration employing an ionic liquid. A clear evolution from superconductor to insulator was observed in nominally 7 unit-cell-thick films. Using a finite size scaling analysis, curves of resistance versus temperature, R(T), over the temperature range from 6 to 22 K were found to collapse onto a single scaling function, which suggests the presence of a quantum critical point.

Aqueous only route toward graphene from graphite oxide.

We report a new, simple, hydrazine-free, high-yield method for producing single-layer graphene sheets. Graphene sheets were formed from graphite oxide by reduction with simple deionized water at 95 °C under atmospheric pressure. Over 65% of the sheets are single graphene layers; the average sheet diameter is 300 nm.