Topologically protected surface Majorana arcs and bulk Weyl fermions in ferromagnetic superconductors

Abstract

A number of ferromagnetic superconductors have been recently discovered which are believed to be in the so-called ``equal spin pairing'' state. In the equal spin pairing state, the Cooper pairs condense forming order parameters ${\ensuremath{\Delta}}_{\ensuremath{\uparrow}\ensuremath{\uparrow}},\phantom{\rule{4pt}{0ex}}{\ensuremath{\Delta}}_{\ensuremath{\downarrow}\ensuremath{\downarrow}}$ which are decoupled in the spin sector. We show that these three-dimensional systems should generically support topologically protected surface Majorana arcs and bulk Weyl fermions as gapless excitations. Similar protected low-energy exotic quasiparticles should also appear in the recently discovered noncentrosymmetric superconductors in the presence of Zeeman splitting. The protected surface arcs can be probed by angle-resolved photoemission as well as Fourier transform scanning tunneling spectroscopy experiments.