Tracking photocarrier-enhanced electron-phonon coupling in nonequilibrium

Light-modulated electron-phonon coupling (EPC) is significant in many intriguing phenomena including light-enhanced superconductivity, polaron formation, and hidden charge orders, which provides a powerful strategy to engineer materials’ functionalities on demand. Here we explore EPC in photoexcited graphene during the ultrafast photocarrier dynamics with a phonon bath. Via analysing energy transport between electrons and phonons, light-induced EPC enhancement by more than one order of magnitude is demonstrated, which originates from the dynamic distribution of photoexcited carriers out of equilibrium. Excellent agreements between theory and experiment have been achieved, justifying the validity of the present approach for extracting excited-state dynamic properties. Our result unravels a crucial impact of photoexcitation on EPC by modulating the density and distribution of photocarriers, and provides a useful strategy for tracking ultrafast EPC in real time.