Electron and spin dynamics in sub-wavelength space-time-intervals

The enormous electric field strength of ultrafast laser waveforms allows to steer electronic motion and control electronic excitation 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 two experiments demonstrating that ultrafast optical fields can manipulate electronic and spin degrees of freedom in solid state systems at clock rates possibly faster than de-coherence. Photodoping the band-structure of wide-gap dielectrics with ultrafast ultraviolet light-fields creates coherent electronic wavepackets that, at early times, can be manipulated by optical gate fields. Before the onset of dissipative processes, this manipulation is entirely reversible, suggesting novel ultrafast, coherent optoelectronic applications. We believe that this speed-up could yield optoelectronic operation up to the Petahertz frontier, which poses the ultimate limit of optoelectronic signal manipulation [1]. 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 onpreviously inaccessible attosecond timescales [2].[1] The speed limit of optoelectronics. In press: Nat. Commun. (2022). doi:10.1038/s41467-022-29252-1[1] Light-wave dynamic control of magnetism. Nature 571, 240–244 (2019)