Exploring the Geometry and Interface Effects in Correlation between Steady-State and Ultrafast Responses of Chiral Plasmonic Nanoparticles.

Chiral plasmonic nanostructures have attracted tremendous attention, but their ultrafast carrier dynamics remain poorly explored compared to steady-state optical properties. Here, we synthesize three types of chiral Au nanoparticles with varying optical dissymmetry factor (g-factors) and different spectral detuning between chiral responses and plasmon resonances. Using chirality-resolved femtosecond transient absorption spectroscopy, we find that hot-carrier cooling dynamics exhibit no measurable dependence on the circular polarization state of pump or probe light within the experimental precision, indicating that macroscopic chiroptical activity does not necessarily translate into handedness-dependent ultrafast carrier dynamics. Furthermore, we show that in bimetallic Au-Ag chiral nanoparticles, the synergy between surface and interface plasmon resonances tunes circular dichroism intensities, while in Au-Ag2S hybrids, interfacial charge transfer largely modulates g-factors. These findings reveal the interplay among structural chirality, chemical interfaces, and hot-carrier relaxation, offering guidelines for designing chiral plasmonic systems.