Attosecond microscopy to track electron and spin dynamics

Attosecond microscopy to track electron and spin dynamics

The enormous electric field strength of ultrafast laser waveforms allows to steer electronic motion so fast, that secondary processes disrupting coherence and striving for an equilibrium have hard time catching up – even in condensed phase systems. We investigate the opportunities this temporal segregation offers to transfer coherent control ideas as demonstrated in atomic and molecular ensembles to solids. This talk will discuss experiments that provide attosecond temporal resolution to show how ultrafast optical fields can manipulate both the electronic and the magnetic state in bulk solids at femtosecond clock rates and provide an insight into recent experimetal developments geared to combine the temporal resolving power of attosecond spectroscopy with sub-wavelength spatial resolution.

Exemplary for coherent quantum manipulation in many-body systems is the capability to launch and track a wavepacket. Photodoping the band-structure of wide-gap dielectrics (as sketched in the figure) with ultrafast ultraviolet light-fields creates such an electronic wavepacket that, at early times, can be manipulated by optical gate fields. Before the onset of dissipative processes, we find this manipulation to be entirely reversible, which we believe could coherent optoelectronic operation up to the Petahertz frontier¹. As a corollary of this ultrafast coherent modification of the electronic system, in suitably chosen heterostructures also the spin system can be manipulated coherently. Optically induced spin transfer is demonstrated as a route to the direct, all-optical manipulation of macroscopic magnetic moments on previously inaccessible attosecond timescales². To extract such dynamical information not only from bulk materials but also from functional heterostructures we are now developing meta-optical nano-focusing elements for attosecond radiation as a first step towards sub-wavelength resolved microscopy in space & time^3.

^1. Ossiander, M. et al. The speed limit of optoelectronics. Nat Commun 13, 1620 (2022).
^2. Siegrist, F. et al. Light-wave dynamic control of magnetism. Nature 571, 240–244 (2019).
^3. Ossiander, M. et al. Extreme ultraviolet metalens by vacuum guiding. Science 380, 59–63 (2023).