Odd triplet superconductivity in a superconductor/ferromagnet system with a spiral magnetic structure

Abstract

We analyze a superconductor-ferromagnet $(S∕F)$ system with a spiral magnetic structure in the ferromagnet F for a weak and strong exchange field. The long-range triplet component (LRTC) penetrating into the ferromagnet over a long distance is calculated for both cases. In the dirty limit (or weak ferromagnetism) we study the LRTC for conical ferromagnets. Its spatial dependence undergoes a qualitative change as a function of the cone angle $\ensuremath{\vartheta}$. At small angles $\ensuremath{\vartheta}$ the LRTC decays in the ferromagnet exponentially in a monotonic way. If the angle $\ensuremath{\vartheta}$ exceeds a certain value, the exponential decay of the LRTC is accompanied by oscillations with a period that depends on $\ensuremath{\vartheta}$. This oscillatory behavior leads to a similar dependence of the Josephson critical current in SFS junctions on the thickness of the $F$ layer. In the case of a strong ferromagnet the LRTC decays over the length which is determined by the wave vector of the magnetic spiral and by the exchange field.