Increased formation of trions and charged biexcitons by above-gap excitation in single-layer $WSe_2$

Abstract

Two-dimensional semiconductors exhibit pronounced many-body effects and intense optical responses due to strong coulombic interactions. Consequently, subtle differences in photoexcitation conditions can strongly influence how the material dissipates energy during thermalization. Here, using multiple excitation spectroscopies, we show that a distinct thermalization pathway emerges at elevated excitation energies, enhancing the formation of trions and charged biexcitons in single-layer WSe2 by up to 2x and 5x, respectively. Power- and temperature-dependent measurements lend insight into the origin of the enhancement. These observations underscore the complexity of excited state relaxation in monolayer semiconductors, provide insight for the continued development of carrier thermalization models, and highlight the potential to precisely control excitonic yields and probe non-equilibrium dynamics in 2D semiconductors.