Colloquium: Excitons in atomically thin transition metal dichalcogenides

Most two-dimensional (2D) semiconductors are interesting materials as quantum confinement enhances the Coulomb interaction between carriers, leading to a strong attraction between conduction electrons and valence holes, forming stable excitons and the optical response of 2D semiconductors can be extraordinary. In this Colloquium the progress and open questions in the study of excitons in 2D semiconductors from both the experimental and theoretical perspectives are reviewed.