Abstract

Understanding the ultrafast dynamics of photoexcited charges in graphene is essential, as the microscopic mechanisms underlying these dynamics determine many of graphene’s optical, optothermal, and optoelectronic properties. Here, dielectric engineering is used to control photoexcited carrier dynamics in monolayer graphene without changing Fermi energy, optical power, or ambient temperature. Optical pump–terahertz probe experiments on graphene in different liquid dielectric environments show that stronger dielectric screening slows both carrier heating and cooling. An analytical model extending hot-carrier thermalization and cooling dynamics reproduces the trends, and calculations indicate that enhanced screening increases mobility and the Seebeck coefficient, implying improved photodetector sensitivity.

Abstract

Understanding the ultrafast dynamics of photoexcited charges in graphene is essential, as the microscopic mechanisms underlying these dynamics determine many of graphene’s optical, optothermal, and optoelectronic properties. Here, dielectric engineering is used to control photoexcited carrier dynamics in monolayer graphene without changing Fermi energy, optical power, or ambient temperature. Optical pump–terahertz probe experiments on graphene in different liquid dielectric environments show that stronger dielectric screening slows both carrier heating and cooling. An analytical model extending hot-carrier thermalization and cooling dynamics reproduces the trends, and calculations indicate that enhanced screening increases mobility and the Seebeck coefficient, implying improved photodetector sensitivity.

Abstract

Understanding the ultrafast dynamics of photoexcited charges in graphene is essential, as the microscopic mechanisms underlying these dynamics determine many of graphene’s optical, optothermal, and optoelectronic properties. Here, dielectric engineering is used to control photoexcited carrier dynamics in monolayer graphene without changing Fermi energy, optical power, or ambient temperature. Optical pump–terahertz probe experiments on graphene in different liquid dielectric environments show that stronger dielectric screening slows both carrier heating and cooling. An analytical model extending hot-carrier thermalization and cooling dynamics reproduces the trends, and calculations indicate that enhanced screening increases mobility and the Seebeck coefficient, implying improved photodetector sensitivity.

Abstract

Understanding the ultrafast dynamics of photoexcited charges in graphene is essential, as the microscopic mechanisms underlying these dynamics determine many of graphene’s optical, optothermal, and optoelectronic properties. Here, dielectric engineering is used to control photoexcited carrier dynamics in monolayer graphene without changing Fermi energy, optical power, or ambient temperature. Optical pump–terahertz probe experiments on graphene in different liquid dielectric environments show that stronger dielectric screening slows both carrier heating and cooling. An analytical model extending hot-carrier thermalization and cooling dynamics reproduces the trends, and calculations indicate that enhanced screening increases mobility and the Seebeck coefficient, implying improved photodetector sensitivity.