Self-balancing luminescence kinetics of charged excitons in WS$_2$ monolayer

Two-dimensional tungsten-based transition metal dichalcogenides exhibit a rich emission spectrum with distinct lines of exciton and biexciton states, neutral and charged, which are typically considered as independent entities. Here, we present a study of the emission kinetics of a WS$_2$ monolayer, demonstrating that these states together form a single interacting ensemble, with their population and depletion mutually coordinated with temperature. Dark trions make a long-lived contribution to the bright trion on a time scale of 200-300 picoseconds, and replenishment from dark states promotes intense luminescence of charged biexcitons. The developed self-consistent rate equation model reproduces the temperature dependence of the kinetics well, opening the way to controlling exciton states in such materials.