Ultrafast investigation of electronic and vibrational dynamics via pump-degenerate four-wave mixing

Phonon dynamics and their coupling to electronic excitations in bulk tungsten disulfide is investigated. Pump-degenerate four-wave mixing is used to measure the femtosecond dynamics of the phonons, which when combined with transient absorption spectroscopy, provides an energy-resolved picture of phonon dynamics and their lifetimes. Measurements suggest the LA(M) phonon mitigates electron scattering from the K point to the Σ valley in under 100 fs. Pump-degenerate four-wave mixing is hereby shown to be an effective tool to compliment momentum-resolved methods for studying coupling in tungsten disulfide and other transition metal dichalcogenides.