Twist-angle tunable bandgap renormalization and exciton binding energy in WS₂ bilayers

The twist angle at van der Waals interfaces has emerged as a powerful degree of freedom for tailoring excitonic energy landscapes in two-dimensional semiconductors, yet how interlayer coupling and photoinduced dynamic dipole screening cooperatively govern excitonic responses remains elusive. Here, we directly investigate the twist-angle-dependent Coulomb-dominated excitonic effects in bilayer WS₂, including bandgap renormalization (BGR), exciton binding energy, recombination lifetime, and mobility. Femtosecond transient absorption spectroscopy reveals a twist-angle-tunable exciton binding energy from 265 to 336 meV; upon approaching the Mott transition threshold, BGR varies by over 100 meV and is most significant near-30°, where weakened interlayer coupling makes Coulomb interactions dominant. Moreover, the exciton lifetime and mobility are jointly dictated by the twist angle: strong interlayer coupling suppresses recombination while enhancing exciton mobility by threefold. This work integrates photoinduced screening with twist-angle engineering, establishing a unified picture of exciton many-body dynamics and offering guidance for high-performance excitonic devices.