Ultrafast nonthermal electron transfer at plasmonic interfaces.

Plasmon-induced charge generation and separation in metal/semiconductor heterostructures offer a promising platform for hot carrier-based energy conversion applications. A key challenge is understanding ultrafast hot carrier transfer at heterogeneous interfaces, as the details of plasmonic enhanced charge transfer dynamics and accompanying energy relaxation remain unclear. Here, by tracking charge transfer processes across spatial, temporal, and energy domains, we reveal ultrafast, nonthermal electron transfer directly from gold nanoparticles to gallium nitride (GaN) without energy losses from electron-electron scattering. This process facilitates efficient charge separation and produces a nonthermal distribution of transferred electron in GaN-contrasting with substantial energy dissipation typically observed during conventional interfacial charge transport. Furthermore, we demonstrate the pivotal role of light polarization in modulating charge generation and energy distribution, which enables dynamic control of electron relaxation and enhances the possibility of nonthermal electrons surmounting the Schottky barrier for successful injection. These insights pave the way for advancing hot-carrier management and achieving coherent control of non-equilibrium charge behavior across multiple dimensions for solar energy conversion and optoelectronic applications.