Energy-resolved hot carrier relaxation dynamics in monocrystalline plasmonic nanoantennas

TL;DR

This study investigates the ultrafast relaxation dynamics of hot carriers in monocrystalline gold nanoantennas, revealing energy-dependent relaxation rates crucial for optimizing hot-carrier applications.

Contribution

It provides the first detailed measurement of hot carrier relaxation times in monocrystalline plasmonic nanoantennas, highlighting their energy dependence and challenging existing multi-photon luminescence interpretations.

Findings

60% variation in relaxation rate for electron-hole energies from 0.2 to 1.8 eV

Nonlinear photoluminescence response varies with hot carrier energy

Relaxation dynamics depend on carrier energy relative to Fermi level

Abstract

Hot carriers are energetic photo-excited carriers driving a large range of chemico-physical mechanisms. At the nanoscale, an efficient generation of these carriers is facilitated by illuminating plasmonic antennas. However, the ultrafast relaxation rate severally impedes their deployment in future hot-carrier based devices. In this paper, we report on the picosecond relaxation dynamics of hot carriers in plasmonic monocrystalline gold nanoantennas. The temporal dynamics of the hot carriers is experimentally investigated by interrogating the nonlinear photoluminescence response of the antenna with a spectrally-resolved two-pulse correlation configuration. We measure time-dependent nonlinearity orders varying from 1 to 8, which challenge the common interpretation of multi-photon gold luminescence. We demonstrate that the relaxation of the photo-excited carriers depends of their energies relative to the Fermi level. We find a 60 % variation in the relaxation rate for electron-hole pair energies ranging from c.a. 0.2 to 1.8 eV. The quantitative relationship between hot carrier energy and relaxation dynamics is an important finding for optimizing hot carriers-assisted processes and shed new light in the intricacy of nonlinear photoluminescence in plasmonic structures.