Ideal spin-polarized Weyl half-semimetal with a single pair of Weyl points in the half-Heusler compounds XCrTe ( X=K , Rb)

Realizing ideal Weyl semimetal state with a single pair of Weyl points has been a long-sought goal in the field of topological semimetals. Here, we reveal such a state in the Cr-based half-Heusler compounds $X\mathrm{CrTe}$ ($X=\mathrm{K}$, Rb). We show that these materials have a half-metal ground state, with the Fermi level crossing only one spin channel. Importantly, the Fermi surface is clean, consisting of the minimal number (i.e., a single pair) of spin-polarized Weyl points, so the state represents an ideal Weyl half-semimetal. We show that the locations of the two Weyl points and the associated Chern vector can be flexibly tuned by rotating the magnetization vector. The minimal surface Fermi arc pattern and its contribution to anomalous Hall transport are discussed. Our finding offers an ideal material platform for exploring magnetic Weyl fermions, which will also facilitate the interplay between Weyl physics and spintronics.