Half- critical current -Oscillations of SQUIDsC. W. Schneider1, G. Hammerl1, G. Logvenov1, T. Kopp1, J. R. Kirtley2, P. J. Hirschfeld3 and J. Mannhart1
1 Experimentalphysik VI, Center for Electronic Correlations and Magnetism Institute of Physics, Augsburg University - D-86135 Augsburg, Germany
2 IBM Thomas J. Watson Research Center - P.O. Box 218 Yorktown Heights, NY 10598, USA
3 Department of Physics, University of Florida - Gainesville, FL 32611, USA
received 3 May 2004; accepted 29 July 2004
The current-voltage characteristics of Superconducting Quantum Interference Devices (SQUIDs) are known to modulate as a function of applied magnetic field with a period of one flux quantum /2e. Here we report on the fabrication and properties of SQUIDs modulating with a fundamental period of . The characteristics of these bicrystal SQUIDs are consistent with either a strong sin(2 ) component of the current-phase relation of the Josephson current, or with an interaction between the Cooper pairs, causing an admixture of quartets to the condensate.
74.20.Rp - Pairing symmetries (other than s-wave).
85.25.Dq - Superconducting quantum interference devices (SQUIDs).
85.25.Cp - Josephson devices.
© EDP Sciences 2004