Surface versus bulk Dirac state tuning in a three-dimensional topological Dirac semimetal

Recently, a crystalline-symmetry-protected three-dimensional (3D) bulk Dirac semimetal phase has been experimentally identified in a stoichiometric high-mobility compound, Cd3As2. The Dirac state observed in Cd3As2 has been attributed to originate mostly from the bulk state while calculations show that the bulk and surface states overlap over the entire Dirac dispersion energy range. In this study we unambiguously reveal doping induced evolution of the ground state of surface and bulk electron dynamics in a 3D Dirac semimetal. The technique demonstrated in this study by simultaneously using angle-resolved photoemission spectroscopy (ARPES) and in situ surface deposition isolates the surface and bulk states in Cd3As2. Our experimental results provide a method for tuning the chemical potential as well as to observe surface states degenerate with bulk states, which will be useful for future applications of a 3D Dirac semimetal.