Low Temperature Physics: 30, 613 (2004); https://doi.org/10.1063/1.1789931 (7 pages)
Физика Низких Температур: Том 30, Выпуск 7-8 (Июль 2004), c. 814-822    ( к оглавлению , назад )

Fractional ac Josephson effect in unconventional superconductors

Hyok-Jon Kwon1, K. Sengupta2, and Victor M. Yakovenko1

1Department of Physics, University of Maryland, College Park, Maryland 20742-4111, USA
E-mail: yakovenk@physics.umd.edu

2Department of Physics, Yale University, New Haven, Connecticut 06520-8120, USA

Received January 5, 2004


For certain orientations of Josephson junctions between two px-wave or two d-wave superconductors, the subgap Andreev bound states produce a 4p-periodic relation between the Josephson current I and the phase difference j: I µ sin( j/2) . Consequently, the ac Josephson current has the fractional frequency eV/ħ where V is the dc voltage. In the tunneling limit, the Josephson current is proportional to the first power (not square) of the electron tunneling amplitude. Thus, the Josephson current between unconventional superconductors is carried by single electrons, rather than by Cooper pairs. The fractional ac Josephson effect can be observed experimentally by measuring frequency spectrum of microwave radiation from the junction.

74.50.+r - Tunneling phenomena; point contacts, weak links, Josephson effects (for SQUIDs, see 85.25.Dq; for Josephson devices, see 85.25.Cp; for Josephson junction arrays, see 74.81.Fa)
74.70.Kn - Organic superconductors
74.72.-h - Cuprate superconductors (high-Tc and insulating parent compounds)