Raman Signatures of Broken Inversion Symmetry and In-plane Anisotropy in Type-II Weyl Semimetal Candidate TaIrTe₄

The layered ternary compound TaIrTe₄ is an important candidate to host the recently predicted type-II Weyl Fermions. However, a direct and definitive proof of the absence of inversion symmetry in this material, a prerequisite for the existence of Weyl Fermions, has not yet been obtained. Herein, an unambiguous identification of the broken inversion symmetry in TaIrTe₄ is established using angle-resolved polarized Raman spectroscopy and first-principle calculations. We also report strong optical anisotropy in TaIrTe₄ crystals, which can be exploited to efficiently and nondestructively determine the exact crystallographic orientation of the material. Such technique could be extended to the fast identification and characterization of other type-II Weyl Fermions candidates. A surprisingly strong in-plane electrical anisotropy in TaIrTe₄ thin flakes is also revealed, up to 200% at 10K. Such strong electrical anisotropy, together with the high carrier density and the environmental stability of the material, may enable new architectures in electrical interconnects in future integrated circuits.