Hund nodal line semimetals: The case of twisted magnetic phase in the double-exchange model*

In this talk, we discuss a class of topological metals, which we dub Hund nodal line semimetals, arising from the strong Coulomb interaction encoded in the Hund's coupling between itinerant electrons and localized spins [1]. We consider a particular twisted spin configuration, which is realized in the double exchange model describing the manganite oxides. As we show, the resulting effective tetragonal lattice of electrons with hoppings tied to the local spin features an antiunitary non-symmorphic symmetry that in turn, together with another non-symmorphic but unitary glide mirror symmetry protects crossings of a double pair of bands along a high-symmetry line on the Brillouin zone boundary. We also discuss the stability of Hund nodal line semimetal with respect to symmetry breaking from various perturbations of the twisted phase. Our results motivate further studies of other realizations of this state of matter, for instance in different spin backgrounds and properties of its drumhead surface states.
[1] R. M. Geilhufe, F. Guinea, and V. Juričić, arXiv:1805.03640.