Half-${h/2\ab{e}}$ critical current —Oscillations of SQUIDs

C. W. Schneider; G. Hammerl; G. Logvenov; T. Kopp; J. R. Kirtley; P. J. Hirschfeld; J. Mannhart

doi:doi:10.1209/epl/i2004-10165-x

Europhys. Lett., 68 (1), pp. 86-92 (2004)
DOI: 10.1209/epl/i2004-10165-x

Half- ${h/2\ab{e}}$ critical current -Oscillations of SQUIDs

C. 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

Abstract
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 $\Phi_0=h$ /2e. Here we report on the fabrication and properties of SQUIDs modulating with a fundamental period of $1/2\times\Phi_0$ . The characteristics of these bicrystal SQUIDs are consistent with either a strong sin(2 $\varphi$ ) 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.

PACS
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

Half- critical current -Oscillations of SQUIDs

Half- ${h/2\ab{e}}$ critical current -Oscillations of SQUIDs