Half-integer Shapiro steps at the 0-pi crossover of a ferromagnetic Josephson junction
Superconductivity
2007-05-23 v1 Mesoscale and Nanoscale Physics
Abstract
We investigate the current-phase relation of S/F/S junctions near the crossover between the 0 and the pi ground states. We use Nb/CuNi/Nb junctions where this crossover is driven both by thickness and temperature. For a certain thickness a non-zero minimum of critical current is observed at the crossover temperature. We analyze this residual supercurrent by applying a high frequency excitation and observe the formation of half-integer Shapiro steps. We attribute these fractional steps to a doubling of the Josephson frequency due to a sin(2*phi) current-phase relation. This phase dependence is explained by the splitting of the energy levels in the ferromagnetic exchange field.
Cite
@article{arxiv.cond-mat/0406236,
title = {Half-integer Shapiro steps at the 0-pi crossover of a ferromagnetic Josephson junction},
author = {H. Sellier and C. Baraduc and F. Lefloch and R. Calemczuk},
journal= {arXiv preprint arXiv:cond-mat/0406236},
year = {2007}
}
Comments
4 pages, 5 figures, accepted for publication in Phys. Rev. Lett