Magnetic topological materials have recently drawn significant importance and interest, due to their topologically nontrivial electronic structure within spontaneous magnetic moments and band inversion. Based on first-principles calculations, we propose that chromium dioxide, in its ferromagnetic pyrite structure, can realize one pair of type-II Weyl points between the Nth and (N+1)th bands, where N is the total number of valence electrons per unit cell. Other Weyl points between the (N−1)th and Nth bands also appear close to the Fermi level due to the complex topological electronic band structure. The symmetry analysis elucidates that the Weyl points arise from a triply-degenerate point splitting due to the mirror reflection symmetry broken in the presence of spin-orbital coupling, which is equivalent to an applied magnetic field along the direction of magnetization. The Weyl points located on the magnetic axis are protected by the three-fold rotational symmetry. The corresponding Fermi arcs projected on both (001) and (110) surfaces are calculated as well and observed clearly. This finding opens a wide range of possible experimental realizations of type-II Weyl fermions in a system with time-reversal breaking.
@article{arxiv.1707.08899,
title = {Ferromagnetic Type-II Weyl Semimetal in Pyrite Chromium Dioxide},
author = {R. Wang and Y. J. Jin and J. Z. Zhao and Z. J. Chen and Y. J. Zhao and H. Xu},
journal= {arXiv preprint arXiv:1707.08899},
year = {2018}
}