ARPES study on a stable three-dimensional topological Dirac semimetal Cd3As2

Three-dimensional topological Dirac semimetal (TDS) is a new state of quantum matter recently proposed and has attracted increasing attention in physics and material science. A 3D TDS not only is a bulk analogue of graphene, but also shows non-trivial topology in its electronic structure. A TDS can also be driven into other novel states with symmetry breaking, making it a unique ``mother compound'' for the study of these states. By performing angle-resolved photoemission spectroscopy, we directly observed a pair of 3D Dirac fermions in Cd3As2, proving that it is a model 3D TDS. Comparing to other 3D TDSs, Cd3As2 is stable and have much higher Fermi velocities. Furthermore, by in-situ doping, we were able to tune its Fermi-energy, making it a flexible platform for exploring exotic physical phenomena and application potentials.