The discovery of quantum materials with non-trivial topological electronic structures has recently ignited intensive interest in physics and materials science. Topological Weyl semimetals (TWSs) represent a new state that that not only possesses Weyl fermions in the bulk and unique Fermi-arcs generated by topological surface states, but also exhibits appealing physical properties such as extremely large magnetoresistance and ultra-high carrier mobility.

In this talk, I will show our angle-resolved photoemission spectroscopy (ARPES) measurement on a recently proposed materials (represented by TaAs), we directly observed the band structures with characteristic Fermi-arcs. In addition, by systematically investigating different compounds from the same material family, we observed the Fermiology evolution with spin-orbit coupling (SOC) strength. The discovery of this family of TWSs provides a rich material base for exploring many exotic physical phenomena and novel future applications.