Johannes Feist Feb 21 Abstract

Controlling electrons and photons on attosecond and nanometer scales

One of the overarching goals of physics is to control light and matter on ever shorter temporal and smaller spatial scales. In the temporal domain, the advent of intense sub-femtosecond ultrashort light pulses has enabled the study of time-resolved electronic processes at their natural timescales in atoms, molecules and solids. In the spatial domain, collective electron-photon oscillations at metal surfaces (surface plasmon polaritons) can concentrate electric fields on sub-wavelength scales of a few nanometers, strongly increasing the interaction between light and matter. I will present our recent work and future prospects in the fields of attosecond science and nanoplasmonics, as well as efforts towards combining these two fields to achieve both temporal and spatial resolution.

In the area of attosecond and strong-field science, I will focus on correlated electronic and nuclear dynamics in simple atoms and molecules in ultrashort pulses. One intriguing example is attosecond streaking, where the timing of electron emission by an extreme-ultraviolet attosecond pulse is mapped to a momentum shift using a synchronized few-cycle infrared pulse. Such a setup can give access to the time delay between different photoionization channels, as well as provide insight into correlated electronic processes in the presence of an infrared field. The rich physics of this process are revealed by accurate numerical simulations for one- and two-electron atoms, which allow creating models that can be extended to many-electron atoms such as neon.

Going one step further, I will discuss the influence of femtosecond-scale nuclear motion on correlated electron dynamics, such as the disappearance of the well-known Fano lineshapes of autoionizing doubly excited resonances in light molecules such as H2.

In the field of nanoplasmonics, I will concentrate on aspects of quantum plasmonics, i.e., the use of plasmonic modes to replace the (cavity) photons typically used in quantum optics. By exploiting their broadband nature and strong field concentration, novel regimes of light-matter interaction can be reached. A canonical example is strong coupling between plasmons and quantum emitters such as organic molecules, leading to the creation of hybrid plasmon-exciton states that combine the properties of both constituents. Due to their ultralight effective mass, these bosonic quasiparticles are prime candidates to achieve condensation, i.e. quantum degeneracy, at room temperature.

Finally, I will discuss some recent works that pursue the combination of nanoplasmonics with attosecond physics. One intriguing aspect is that due to the electric field concentration at plasmonic structures, even a low-power laser pulse can be locally amplified to reach the regime of strong-field physics. This opens the way to the use of coherent control techniques to tailor the electric field response of the plasmon, which could lead to new applications such as producing isolated attosecond pulses using much weaker driving lasers than typically necessary.