Weyl semimetal phase in the noncentrosymmetric superlattice W2XY(X,Y=S,Se,Te,X≠Y)

We investigated the topological properties and strain modulation of transition-metal monochalcogenides ${\mathrm{W}}₂XY(X,Y=\mathrm{S},\phantom{\rule{0.16em}{0ex}}\mathrm{Se},\phantom{\rule{0.16em}{0ex}}\mathrm{Te},X\ensuremath{\ne}Y)$ by combining the first-principles method and the Wannier-based tight-binding method. The number and chirality of Weyl node, surface spectra, and surface Fermi arcs are calculated to identify their topological properties. The ${\mathrm{W}}₂XY$ compounds are nodal line semimetals in the absence of spin-orbit coupling (SOC). When SOC turns on, the nodal lines split into 24 Weyl nodes on the ${k}_z\ensuremath{\ne}0$ planes, which are related by time-reversal, ${C}_{3\mathrm{z}}$ rotational, and mirror symmetries. Weyl points' energies are close to the Fermi level and the maximal separation between two Weyl points with opposite handedness in reciprocal space is on the order of magnitude of $0.1\phantom{\rule{0.16em}{0ex}}{\AA{}}^{\ensuremath{-}1}$, which can be accessed by angle-resolved photoemission spectroscopy. Interestingly, the Weyl semimetal phase exhibits great robustness and asymmetric response under uniaxial/biaxial compression and tensile strain. The positions of Weyl points change significantly and lead to a striking modulation of topological properties under in-plane biaxial strain. These findings are important for studying the behavior of Weyl fermions in layered materials and useful for realizing their applications in topological electronic devices.