Előadó: Pápa Zsuzsanna (SZFI, ELI-ALPS)
Az előadás témája: Ultrafast Probing of Electron Occupancies of Nanoplasmonic Systems
Az előadás időpontja: 2020. december 1., kedd, 10.00
Helyszín: videokonferencia, https://letsmeet.wigner.hu/szeminarium
Plasmonic systems are of great interest due to the nanometric volumes and ultrafast timescales involved during their excitation and decay. Upon the absorption of a photon, energy is transferred to the electrons in the metal, thus driving the electron distribution out of equilibrium. As time evolves on fs scale, a series of energy redistributions occur where energetic electrons first scatter among themselves and redistribute their energy until a high temperature Fermi–Dirac distribution is reached on the scale of hundreds of femtoseconds. Electron–phonon interactions then lead to a gradual reduction of this electronic temperature on a picosecond time scale. Due to the surface-bound nature of plasmons, these light-matter interaction processes are also worth examining from a new perspective. As the electron occupancies change during the various processes described above so does the dielectric function. This means that it is possible to retrieve electron occupancies and electron energy levels at different stages of plasmon excitation and decay by measuring the dielectric function of the plasmonic system in a highly sensitive way. In this presentation, I will report on a new tool for ultrasensitive probing of plasmonic hot electron occupancies in gold, applying ultrafast pump-probe spectroscopic ellipsometry.