Creating triplet superconductivity in artificial metallic heterostruct…

" Superfluidity does not necessarily require a spin singlet state for a pair of fermions as the ground state, although the BCS theory of superconductivity assumes singlet pairing.For example, in 3He superfluid, a spin triplet state was found to be possible. In solid state materials, there have been reports of triplet superconductivity in some heavy fermion materials and, recently, in Sr2RuO4. Here we report on Tc behavior of Nb/Au(Al)/CoFetrilayers with respect to d_Au(Al) and d_CoFe, respectively. We show our results cannot be explained by the current theories based on singlet superconductivity and, instead, support the existence of triplet superconductivity in these artificial metallic heterostructures. Spin triplet states in artificial structures could pave a way to studying this interesting phenomenon in a systematic and controlled fashion. "