Magnetic edge states and mixed-parity pairing in spin-triplet superconductors

We show that a spontaneous magnetic moment may appear at the edge of a spin-triplet superconductor if the system allows for pairing in a subdominant channel and non-uniform spatial profile. To unveil the microscopic mechanism behind such effect we combine numerical solution of the Bogoliubov-De Gennes equations for a tight-binding model with nearest-neighbor attraction, and the symmetry based Ginzburg-Landau approach. We find that a modulation of the electronic density near the edge of the system leads to a non-unitary superconducting state where spin-singlet pairing coexists with the dominant triplet superconducting order. We demonstrate that the spin polarization at the edge appears due to the inhomogeneity of the non-unitary state and originates in the lifting of the spin-degeneracy of the Andreev bound-states. For chiral spin-triplet superconductors spin current flows along the interface and surface charge currents exhibit anomalous dependence on the magnetization. - A. Romano, P. Gentile, C. Noce, I. Vekhter, M. Cuoco, Phys. Rev. Lett. 110, 267002 (2013).