Coherent manipulation of the electronic structure via controlling the electron-phonon coupling in BaF₂ crystal

The electron-phonon coupling (EPC) is a universal interaction in condensed systems and plays a vital role in shaping the electronic properties of materials, which results in the potential for tailoring material properties and enabling innovative applications for future devices. However, achieving coherent manipulation of electronic structure via the EPC has proven to be challenging. Here, using the time-resolved High harmonic generation (tr-HHG) spectroscopy technique, we demonstrate the coherent manipulation of electronic structure in BaF₂ crystal through precise control of EPC by ultrashort light pulses, specifically by changing the relative polarization orientation, ellipticity, and strength of the pump light field. Combined with quantum modeling via including the EPC and density functional theory from first principles, we reproduce the observed 2D modulated tr-HHG spectra accordingly. Our results reveal that carefully tuning the lattice dynamics through a coherent external light field can effectively control the strength and excitation initial phase of the EPC in BaF₂. This control over EPC allows us to coherently modify the electronic band structure, both in the initial phase and amplitude, resulting in altering carrier transport properties and inducing possible novel quantum phenomena. Our findings provide a solid foundation for future studies aiming to harness and exploit the EPC in other materials systems.