"Hot" carriers in nanostructures – when they matter, and when they do not...

In the last couple of decades, non-thermal (“hot”) carriers in nanostructures have been simultaneously an inspirational concept to which a series of effects were ascribed, but also a source of confusion and hot debates. My talk will be aimed at describing the advances we obtained in the understanding of the role played by “hot” carriers in metals via rigorous modelling of their generation process and dynamics, and extensive comparison to previous and new experimental work. I will start by presenting a self-consistent theory of the steady-state electron distribution in metals under continuous-wave illumination which treats, for the first time, both thermal and non-thermal effects on the same footing. I will show that the deviation from thermal equilibrium is very weak, so that only a tiny fraction of the absorbed energy ends up generating these non-thermal electron while the rest simply causes heating [1]. I will then review in detail recent experimental quantitative confirmations of our theory obtained in current measurements through plasmonic molecular and tunnel junctions [2]. Then, I shall discuss reports of observation of nonthermal electrons in two classes of experiments. First, I will review briefly our (unfortunately discouraging...) re-interpretation of previous claims of the possibility to enhance chemical reactions with non-thermal electrons from metals as nothing but pure thermal effects [3]. Then, I will show that non-thermal electrons do manifest themselves in metal photoluminescence experiments, and resolve several decade-long associated disagreements in the literature [4].

References
[1] Dubi & Sivan, Light: Science & Applications 8, 89 (2019).
[2] Dubi, Un & Sivan, Nano Letters 22, 2127 (2022); Lin et
al., ACS Photonics 10, 3637 (2023).
[3] Sivan & Dubi, Applied Physics Letters: Perspectives 117,
130501 (2020).
[4] Sivan & Dubi, ACS Nano 15, 8724 (2021).