G. Mohammadkhani | Searcharxiv

arXiv2007

Magnetic interference pattern in planar SNS Josephson junctions

We study the Josephson current through a ballistic normal metal layer of thickness $D$ on which two superconducting electrodes are deposited within a distance $L$ of each other. In the presence of an ({\it in-layer}) magnetic field we find that the oscillations of the critical current $I_c(Φ)$ with the magnetic flux $Φ$ are significantly different from an ordinary magnetic interference pattern. Depending on the ratio $L/D$ and temperature, $I_c(Φ)$-oscillations can have a period smaller than flux quantum $Φ_0$, nonzero minima and damping rate much smaller than $1/Φ$. Similar anomalous magnetic interference pattern was recently observed experimentally.

cond-mat.supr-con↗

arXiv2006

Nonsinusoidal current-phase relations and the $0-π$ transition in diffusive ferromagnetic Josephson junctions

We study the effect of the interfacial transparency on the Josephson current in a diffusive ferromagnetic contact between two superconductors. In contrast to the cases of the fully transparent and the low-transparency interfaces, the current-phase relation is shown to be nonsinusoidal for a finite transparency. It is demonstrated that even for the nearly fully transparent interfaces the small corrections due to weak interfacial disorders contribute a small second-harmonic component in the current-phase relation. For a certain thicknesses of the ferromagnetic contact and the exchange field this can lead to a tiny minimum supercurrent at the crossover between 0 and $π$ states of the junction. Our theory has a satisfactory agreement with the recent experiments in which a finite supercurrent was observed at the transition temperature. We further explain the possibility for observation of a large residual supercurrent if the interfaces have an intermediate transparency.

cond-mat.mes-hall↗