Angle-resolved photoemission spectroscopy studies of topological semimetals

Topological semimetals (TSMs) are a class of novel quantum materials with gapless bulk band crossings and characteristic surface states protected by nontrivial topology. Based on the dimension and degeneracy of band crossings, TSMs can be divided into zero-dimensional four-folding degenerate Dirac, two-folding degenerate Weyl, three-/six-/ eight-folding degenerate, and high-dimensional nodal-line/surface semimetals. In the past decade, researchers have measured the bulk band crossings and characteristic surface states of TSMs through angle-resolved photoemission spectroscopy (ARPES) to clearly reveal the topological nature of these TSMs. In this article, we systematically review the achievements and advances of ARPES studies of TSMs. This review will help us understand the physical properties and topological origins and facilitate the exploration of more novel TSMs.