Non-uniform superconductivity and Josephson effect in conical ferromagnet

Research paper by Hao Meng, A. V. Samokhvalov, A. I. Buzdin

Indexed on: 21 Dec '18Published on: 21 Dec '18Published in: arXiv - Physics - Superconductivity

Abstract

Using the Gorkov's equations we provide an exact solution for a 1D model of superconductivity in the presence of conical helicoidal exchange field. Due to the special type of the symmetry of the system the superconducting transition always occurs into a non-uniform superconducting phase (in contrast with Fulde-Ferrell-Larkin-Ovchinnikov state, which appears only at low temperatures). We directly demonstrate that the uniform superconducting state in our model carry a current and thus does not correspond to the ground state. We study in the framework of Bogolubov-de-Gennes approach the properties of the Josephson junction with a conical ferromagnet as a weak link. In our numerical calculations, we do not use any approximations (like e.g. a quasiclassical approach) and show a realization of anomalous $\phi_{0}$-junction (with a spontaneous phase difference $\phi_{0}$ in the ground state). The spontaneous phase difference $\phi_{0}$ strongly increases at high values of the exchange field near the borderline with a half-metal and exists also in the half-metal regime.