The orbital-driven topological phase transition and planar Hall responses in ternary tellurides Weyl semi-metals

Here we study electronic properties of the ternary tellurides TaXTe$_4$ (X=Rh, Ir) using density functional theory and investigate chiral anomaly mediated planar Hall response from ab initio calculations. We show that TaRhTe$_4$ is a hybrid Weyl semimetal (WSM), hosting Weyl points (WPs) of both type-I, type-II, while TaIrTe$_4$ is a type-II WSM as it hosts only type-II WPs with spin-orbit couplings (SOC). All WPs lie in the $k_z=0$ plane, and remain well-separated in both momentum and energy landscape. We observe long Fermi arcs connecting Weyl nodes of opposite chirality. We report both SOC and orbital driven topological phase transition in ternary tellurides. TaIrTe$_4$ undergoes topological phase transition under SOC. Whereas orbital driven topological phase transition due to d$_{xz}$ orbital has been observed in TaRhTe$_4$ even without SOC. Furthermore, the evolution of the band structures and the annihilation of WPs due to d$_{xz}$-Ir/Rh orbitals associated with the phase transitions in TaXTe$_4$ are also discussed. This systematic study opens new routes for engineering topological materials relying beyond strong SOC and sheds light on the possible role of correlation effects originating from orbital orbital degree of freedoms in tellurides. We further report an enhancement of planar Hall effects due to orbital driven topological phase transition in TaXTe$_4$ and we make resort to a tight-binding model to correlate the above findings with the effective mass anisotropy in different types of WSMs.