Abstract

Time-resolved photoemission combines femtosecond pump-probe techniques with angle-resolved photoelectron spectroscopy (ARPES). Recent developments enable the method to access the strong-field regime of light-matter interaction and track electron motion in two-dimensional momentum space with subcycle time resolution. In this talk, I will briefly introduce the state-of-the-art of the method and discuss a couple of examples from our recent work. These include bandstructure videography of lightwave-induced quasi-relativistiv currents in graphene and in topologically protected surface states [1,2], of the birth and collapse of Floquet-Bloch states [3], and of the formation of dark excitons in 2D semiconductors [4]. Finally, I will outline the perspectives of photoemission orbital tomography [5] to take slow-motion movies of molecular orbitals while they are driven by lightwaves.

References
[1] J. Reimann et al., “Subcycle observation of lightwave-driven Dirac currents”, Nature 562, 396 (2018)
[2] V. Eggers et al., “Subcycle band-structure videography of lightwave-controlled electrons in graphene”, in preparation
[3] S. Ito et al., “Ultrafast birth, rise, and collapse of a Floquet-Bloch band structure”, Nature 616, 696 (2023)
[4] R. Wallauer et al., “Momentum-resolved exciton formation dynamics in monolayer WS2”, Nano. Lett. 21, 5867 (2021)
[5] R. Wallauer et al., “Tracing orbital images on ultrafast time scales”, Science 371, 1056 (2021)