Josephson, Brian David

(1940– ) British theoretical physicist: discovered tunnelling between superconductors.

Josephson studied at Cambridge and remained to become a professor of physics (1974). He discovered the Josephson effect while still a research student (1962), by considering two superconducting regions separated by a thin region of insulator (perhaps 1–2 nm thick). He showed theoretically that a current can flow between the two with no applied voltage as a result of electron tunnelling and that when a DC voltage is applied an AC current of frequency proportional to the voltage is produced. Experimental verification of this effect by J M Rowell and at Bell Telephone Laboratories supported the BCS theory which Josephson had used. The application of a small magnetic field across the junction sensitively alters the current. Such Josephson junctions have been used to measure accurately h/e , voltage and magnetic fields, and in fast switching devices for computers. Josephson shared a Nobel Prize in 1973. Since then his interests have moved to psychic phenomena and to music.