Weyl fermions in ferromagnetic high-temperature phase of K2Cr8O16

Abstract

By combining first-principles calculations and symmetry arguments, we propose that the half-metallic phase of K _2 Cr _8 O _16 presents ferromagnetic Weyl fermions. In particular, K _2 Cr _8 O _16 possesses two pairs of Weyl nodes, which originate from two groups of nodal lines connected by the mirror reflection symmetry. We show that the non-trivial topological properties of K _2 Cr _8 O _16 come from the partially occupied t _2g states of Cr, and we also demonstrate that such exotic topological feature is robust. The topological surface states and corresponding Fermi arcs are revealed. As K _2 Cr _8 O _16 is a realistic and widely studied material, our results suggest that K _2 Cr _8 O _16 is an ideal candidate for studying ferromagnetic Weyl fermions. In addition, K _2 Cr _8 O _16 possesses several interesting phenomena, such as the co-existence of charge density wave and Weyl fermions, even pairs of FM Weyl points, and tunable distribution of Weyl points, which will attract intensive attentions in this field.

Keywords

• topological material
• Weyl semimetal
• magnetic topological semimetal