Supercurrent Switch in Graphene $\pi$ Junctions

We study the supercurrent in a superconductor/ferromagnet/superconductor graphene junction. In contrast to its metallic counterpart, the oscillating critical current in our setup decays only weakly upon increasing the exchange field and junction width. We find an unusually large residual value of the supercurrent at the oscillatory cusps due to a strong deviation from a sinusoidal current-phase relationship. Our findings suggest a very efficient device for dissipationless supercurrent switching.

Figure 1

Contour plot of the Andreev bound states in the ferromagnetic region carrying the current between the superconductors.

Figure 2

(a) Current-phase relationship in the S/F/S graphene junction with an undoped F region. We have fixed ${\epsilon }_F=h$ and set ${\epsilon }_F^{\prime }=0$. We have used values of $P$ in the interval [0.0, 1.2] in steps of 0.2. (b) Current-phase relationship in the S/F/S graphene junction with a doped F region. We have set ${\epsilon }_F/{\Delta }_0=10$, ${\epsilon }_F^{\prime }/{\Delta }_0=15$, and $d/\xi =0.05$ and vary $h/{\Delta }_0$ in the range [0, 5] in steps of 1.

Figure 3

The critical supercurrent in a proximity-induced S/F/S graphene junction for ${\epsilon }_F=h$ and ${\epsilon }_F^{\prime }=0$.