Novel topological excitations: Type-II Weyl fermions and more
In recent years it was realized that our knowledge of possible quasiparticle excitations is incomplete even for non-interacting systems. I will talk about several novel topological excitations that appear in metals. One of them realizes a new type (type-II) of Weyl fermion, hosting the behavior very different from its standard quantum field theory counterpart. In particular, we predict a new type of the chiral anomaly to appear in type-II Weyl metals. The second phase is that of a “dirty” Weyl point, where a Weyl point coexists with an additional electronic state, still topologically protected and producing Fermi arcs on the material’s surfaces. Finally, I will introduce a novel nodal chain phase, that is predicted to exhibit a variety of non-standard behavior in magnetic fields. Real material examples will be presented for all the above phases.