First-Principles Prediction of New Magnetic Weyl Semimetals: Cobalt-Based Shandites System

The experimental confirmation of Co₃Sn₂S₂ as the first magnetic Weyl semimetal (MWSM) paved the way to explore new magnetic Weyl semimetals. Cobalt-based shandite consists of T₃M₂X₂ (T = Co; M = Ge, Sn, Pb; X = S, Se) in a rhombohedral arrangement with rotational symmetry, inversion symmetry, and a kagome layer formed by Co. Using a first-principles approach coupled with a global structure search algorithm, we explored energetically stable configurations of Co-based shandites and their alloys (T₃M₁M₂X₂, where M1/M2 = Ge, Sn, and Pb). We characterized their electronic properties by establishing a tight-binding Hamiltonian with parameters extracted from maximally localized Wannier functions,and identified new MWSMs. The Weyl points of new MWSMs are formed by p-orbital of elements M located between the kagome layer and d-orbitals of Co on the kagome layer, where their location and energy level changes as a function of M. A wider class of new MWSMs that can be synthesized experimentally is proposed.