  Weyl semimetals are a new member of the topological materials family,
featuring a pair of singly degenerate Weyl cones with linear dispersion around
the nodes in the bulk, and Fermi arcs on the surface. Depending on whether the
system conserves or violates Lorentz symmetry, Weyl semimetals can be
categorized into two classes. Photoemission spectroscopy measurements have
confirmed the TaAs-class and WTe2-class of Weyl semimetals as type-I and
type-II respectively. This review article aims to elucidate and elaborate on
the basic concepts of Weyl semimetals and quasiparticle interference
experiments on both type-I and type-II Weyl semimetals. The versatile results
which reveal (1) the topological sink effect of the surface carriers, the
unique feature of the Fermi arc state; (2) the weakly bound nature of the Fermi
arc surface state; (3) the orbital dependent scattering channels on the
surface; (4) a mirror symmetry protected surface Dirac cone, are summarily
discussed. Finally, a perspective toward the future applications of
quasiparticle interference techniques on topological materials is presented.
