We aim to advance time-resolved photoelectron spectroscopy to nano-scale monitoring of electromagnetic fields on surfaces up to Petahertz frequencies by using waveform-controlled near-single-cycle and synthesized sub-cycle laser fields. Major aims include the exploration of the propagation and control of surface plasmon waves at nanoscaled metal-dielectric interfaces, where plasmon coupling, interference and switching can be coherently controlled by the spatial and temporal phase of the controlling light field.
Photoemission from solids is one of the most fundamental and long-studied electron phenomena in nature. Related photon-electron interactions form the basis for modern optoelectronics, where light can trigger electron transfer, amplification, and emission. Yet, with electronic and optoelectronic circuitry in nanometer dimensions, a comprehensive insight into electron dynamics on this spatial scale, in particular in strong fields, has remained elusive. An essential prerequisite for a thorough understanding of nanoscale collective electron motion, which we aim to achieve, is the ability to characterize optical near-fields with sub-cycle, i.e. attosecond temporal resolution.
Achieving ultrafast control of electronic currents in nanowires and nanowire-nanotip heterostructures is an important objective, which we investigate in collaboration with Peter Hommelhoff (Erlangen University). Plasmon and current propagation through nanowires serves as an ultrafast transport system and is thus a crucial ingredient for petahertz electronics. In contrast to bulk solids, nanowires exhibit a longer mean free path for the inelastic scattering of electrons and support quasi-ballistic electron motion. Tailored light sources will be used to control the amplitude and directionality of such currents with the pulse waveform. The parallel development of a high-repetition rate (100 kHz) light source within the MAP “Ultrafast Nanophotonics” group provides much higher photoelectron signals and importantly permits to study the dynamics from the single-electron emission to the many-electron emission regime. This high repetition rate will facilitate the direct measurement of the current through a single nanowire.
Our research is centrally embedded into the B3 area, where the basic optical tools and hardware building blocks for petahertz nanoelectronics are being developed, in order to demonstrate the ultrafast processing potential of nanocircuits controlled by broadband, tailored lightwaves. Our project is the link between individual efforts in B3.1 in generating tailored light waves, in B3.2 in investigating the nonlinear response of solids in strong fields, in B3.4 in imaging electron dynamics with high resolution. Finally yet importantly, the developed infrastructure is relevant also for coincidence studies on the dynamics in molecules and molecule/nanostructure interfaces conducted in close collaboration with the B2 area, theoretically supported by Regina de Vivie-Riedle.