Quasi-Flat-Band in s1/s2 Pyrochlore Oxides and the Effect of Spin-Orbit Interaction

Abstract An isotropic tight-binding model with the nearest-neighbour hopping on a pyrochlore lattice gives rich variety of physical properties due to emergence flat-band. Moreover, by introducing spin-orbit coupling into this model, topological system changes significantly. This is well applicable some oxides called s1/s2 pyrochlores. In paper we apply an s2 oxide Pb 2 Ta O 7 and found characteristic quadratic touching quasi-flat band dispersive band. Furthermore, when ferromagnetic order appears band, pair Weyl points in that direction.