Real-time tracking of interfacial charge dynamics in a metal-dielectric Janus nanocluster

Plasmon-driven charge transfer at metal-dielectric interfaces plays a central role in hot-carrier optoelectronics and photocatalysis. Here we investigate ultrafast electron dynamics in a finite Janus Au-Si nanocluster using real-time time-dependent density functional theory. By combining energy-, time-, and space-resolved analyses, we correlate optical excitation pathways with induced charge density and interfacial carrier redistribution. Energy-resolved carrier distributions reveal that photoexcited electrons are preferentially redistributed into the Si region via near-Fermi-level transitions, while holes remain largely localized within the Au component. The Si-projected density of states exhibits finite weight at the Fermi level, indicating the presence of metal-induced and hybridized interface states in this strongly coupled nanoscale heterostructure. As a consequence, the Si-projected carrier population does not display a sharp conduction-band onset, and the dominant excitation channels occur within a few tenths of an electronvolt above the Fermi level. We emphasize that these results describe the initial, coherent electronic response on ultrafast time scales in an isolated system, and do not include electron-phonon scattering, thermalization, or carrier extraction processes. These results illustrate how, in finite Janus metal-dielectric nanostructures, plasmon-assisted interfacial hybridization can facilitate low-energy carrier redistribution that differs from the classical over-the-barrier hot-electron transport picture.