Evolution of Weyl nodes in Ni-doped thallium niobate pyrochlore Tl2−xNixNb2O7

Magnetic Weyl semimetal (WSM) is of great importance both for fundamental physics and potential applications due to its spontaneous magnetism, robust band topology, enhanced Berry curvature. It possesses many unique quantum effects, including large intrinsic anomalous Hall effect, Fermi arcs, chiral anomaly. In this work, using ab initio calculations, we propose that Ni doped pyrochlore Tl$_2$Nb$_2$O$_7$ a magnetic WSM caused by exchange field splitting on bands around quadratic crossing point. The tuned 3d on-site Coulomb interaction parameter $U$ drives the evolution nodes resulting topological phase transition. Since can exist at generic point in Brillouin zone are hard be exactly identified, creation annihilation them, i.e., change their number, chirality distribution, have been consistently confirmed with combined theoretical approach, which employs parity criterion, symmetry indicator analysis Wilson loop Wannier center. We find remain quite range close level, makes experimental observation very possible. think method our proposal will useful finding more WSMs adding understanding