Project title: Hot electrons in nanoplasmonics: combining quantum mechanics with nanophotonics

Supervisors: Dr Ortwin Hess and Dr Johannes Lischner

Project description:

The illumination of a metallic surface with light triggers a set of processes that include the generation of hot carriers, the re-emission of photons or the excitation of a plasmon. In general, a small fraction of the incident light is absorbed by the metal surface. For metallic nanostructures, absorption can be enhanced by exciting surface plasmons. The excitation of a surface plasmon occurs at the surface of a conductor by the resonant interaction of the collective oscillations of free electrons with light. When these oscillations take place in metallic nanostructures they enable us to manipulate light with nanometer scale precision in the femtosecond time regime. Plasmons can decay emitting a photon or producing electron-hole pairs. These are referred to as hot carriers when their energies are larger than the thermal energy excitations at room temperature.
In the recent years, the study of the generation of hot carriers after the decay of a plasmon has become a matter of interest due to its many applications. They can be injected into a semiconductor and used in photovoltaics [1] or induce chemical reactions that are usually energetically demanding, such as the dissociation of the H2 molecule at room temperature at the surface of a gold nanoparticle [2].

Despite the promising energy conversion mechanism due to hot electron generation, a comprehensive theoretical model that fully explains the phenomenon is missing. The goal is to develop new methods for modelling the time evolution of nanoplasmonics beyond the linear response regime that could include time-dependent density matrix approaches or non-equilibrium Green’s functions to treat dynamically the hot carrier generation after the decay of a plasmon in a metallic nanoparticle.

[1] C. Clavero. Plasmon-induced hot-electron generation at nanoparticle/metal-oxide interfaces for photovoltaic and photocatalytic devices. Nature Photonics, 2014.

[2] Halas N. J., Brongersma, M.L. and P. Nordlander. Plasmon-induced hot carrier science and technology. Nature Nanotechnology, 2015