Weyl fermion is a massless Dirac fermion with definite chirality, which has been long
pursued since 1929. Though it has not been observed as a fundamental particle in nature,
Weyl fermion can be realized as low-energy excitation around Weyl point in Weyl semimetal,
which possesses Weyl fermion cones in the bulk and nontrivial Fermi arc states on the
surface. As a firstly discovered Weyl semimetal, TaAs crystal possesses 12 pairs of Weyl
points in the momentum space, which are topologically protected against small …