Polymer film effect is basis of molecular switch

Researchers at the University of Texas, Austin, have discovered that a thin-film superconductor's ability to carry electrical current with zero resistance can be modulated (weakened or strengthened) in a controllable and reproducible manner by altering the oxidation state of an organic polymer film that is in contact with the superconductor. The effect thus forms the basis of a new type of molecular switch for controlling superconductivity. The new type of switch consists of a superconductor microbridge coated with a conducting polymer. It is made by first depositing a thin film of the superconductor YBa[sub 2]Cu[sub 3]O[sub 7 [minus] [delta]] on a magnesium oxide substrate no larger than 1 cm square using a laser ablation method. An excimer laser or a diamond-tipped micromanipulator is then used to remove the superconductor film from parts of the substrate so that only a thin strip of the cuprate (about 3 mm long and 100 [mu]m wide) connects the larger cuprate regions. Electrical contacts are attached to the superconductor film, which is then masked with wax (except for the microbridge). This allow a thin layer of conductive polymer to be electrochemically deposited only on the exposed microbridge.