Highly Anisotropic Drude‐Weight‐Reduction and Enhanced Linear‐Dichroism in van der Waals Weyl Semimetal <i>T_d</i>‐MoTe₂ with Coherent Interlayer Electronic Transport

Abstract Weyl semimetal (WSM) states can be achieved by breaking spatial‐inversion symmetry or time reversal symmetry. However, the anisotropy of the energy reduction contributing to the emergence of WSM states has seldom been investigated by experiments. A van der Waals metal MoTe 2 exhibits a type‐II WSM phase below the monoclinic‐to‐orthorhombic‐phase‐transition temperature T c ∼ 250 K. Here, a combined linearly polarized optical‐spectroscopy and electrical‐transport study of MoTe 2 is reported at different temperatures. The Drude components in the a ‐axis, b ‐axis, and c ‐axis optical conductivity spectra, together with the metallic out‐of‐plane and in‐plane electrical resistivities, indicate the coherent inter‐layer and in‐plane charge transports. Moreover, the Drude weight in σ 1 a ( ω ), rather than the Drude weights in σ 1 b ( ω ) and σ 1 c ( ω ), decreases dramatically below T c , which exhibits a highly anisotropic decrease in its Drude weight and thus suggests a strongly anisotropic reduction of the electronic kinetic energy in the WSM phase. Furthermore, below T c , due to the in‐plane anisotropic spectral‐weight transfer from Drude component to high‐energy region, the in‐plane inter‐band‐absorption anisotropy increases remarkably ≈770 meV, and has the largest value (≈0.68) of normalized linear dichroism among the reported type‐II WSMs. The work sheds light on seeking new WSMs and developing novel photonic devices based on WSMs.