Fundamental limits of hot carrier injection from metal in nanoplasmonics

TL;DR

This paper analyzes the quantum processes governing hot carrier generation and injection in metal nanoplasmonics, highlighting fundamental limits and proposing strategies to enhance plasmonic device efficiency.

Contribution

It provides a detailed quantum-mechanical description of carrier dynamics and identifies key factors affecting injection efficiency in nanoplasmonic systems.

Findings

Carrier generation is a quantum process with at most one SPP per nanoparticle.

Non-equilibrium carriers not scattered by electron-electron interactions dominate injection.

Relaxing momentum conservation rules shifts the efficiency dependence to the density of states.

Abstract

Evolution of the nonequilibrium carriers excited in the process of decay of surface plasmon polaritons in metal is described for each step, from the carrier generation to their extraction from the metal. The relative importance of various carrier generating mechanism is discussed. It is shown that both carrier generation and their decay are inherently quantum processes as for realistic illumination conditions no more than a single SPP per nanoparticle exists at a given time. As a result, the distribution of non-equilibrium carriers cannot be described by a single temperature. It is also shown that the originally excited carriers that have not undergone a single electron-electron scattering event, are practically the only ones that contribute to the injection. The role of the momentum conservation in the carrier extraction is discussed and it is shown that if all the momentum conservation rules are relaxed, it is the density of states in the semiconductor/dielectric that determines the ultimate injection efficiency. A set of recommendations aimed at improving the efficiency of plasmonic-assisted photodetection and (to a lesser degree) photocatalysis is made in the end.