Berry curvature and orbital angular momentum of electrons in angle-resolved photoemission spectroscopy

摘要

Berry curvature of Bloch wave functions in solids plays important roles in a variety of phenomena, and its integral over the Brillouin zone defines the topological index. However, the direct observation of the Berry curvature in momentum space has been missing. Here we show theoretically that the Berry curvature of the spin wave function can be detected through the orbital angular momentum of the emitted electrons in angle-resolved photoemission spectroscopy when the beam size of the incident light is small enough. As a representative example, the Dirac fermion on the surface of a topological insulator is investigated, and the feasibility of the observation is discussed. This finding will pave a new route to study the topological nature of electronic states in solids.