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 Φ0=h/2e. Here we report on the fabrication and properties of SQUIDs modulating with a period of 1/2×Φ0. The characteristics of these bicrystal SQUIDs are consistent with either a strong sin(2ϕ) 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.
@article{arxiv.cond-mat/0403595,
title = {Half - h/2e - Oscillations of SQUIDs},
author = {C. W. Schneider and G. Hammerl and G. Logvenov and T. Kopp and J. R. Kirtley and P. J. Hirschfeld and J. Mannhart},
journal= {arXiv preprint arXiv:cond-mat/0403595},
year = {2007}
}