Chemical requirements for stabilizing type-II Weyl points in MnBi2-xSbxTe4

We show that type-II Weyl point formation in MnBi2-xSbxTe4 is more likely than in MnBi2Te4 when x reaches 0.5, as the alloy case does not suffer from the same degree of lattice parameter sensitivity as in MnBi2Te4. To further substantiate the stability of type-II Weyl points in MnBi2-xSbxTe4, we demonstrate that among the three conditions of establishing a type-II Weyl point, two are robustly satisfied by the zone-folded dispersion of Bi and Te pz orbitals and spin-orbit coupling already available in MnBi2Te4, and that the control over MnBi2-xSbxTe4 alloy composition provides a rational means to satisfy the third condition. The stability of type-II Weyl points in MnBi1.5Sb0.5Te4 is thus intimately associated with orbital interactions, providing a concrete foundation for future efforts in band engineering and the rational design of topological electronic structures.