Theory of Exciton–Exciton Interactions in Monolayer Transition Metal Dichalcogenides

Two‐dimensional layers of transition metal dichalcogenides (TMDCs) represent semiconductors with a complex single‐particle bandstructure and reduce screening of the three‐dimensional Coulomb interaction. The efficient Coulomb interaction causes optical excitations close to the band edge to be dominated by strongly correlated, bound electron–hole pairs, called excitons. Here, a theoretical formalism is presented to efficiently describe the optical dynamics of atomically thin TMDCs in a naturally adapted two particle exciton basis. As an example, Coulomb intravalley coupling, intervalley exchange, as well as intrinsic and Dexter‐like intervalley interactions are discussed in Hartree–Fock approximation.