Würzburg ToCoTronics Colloquium

Angle-resolved photoemission spectroscopy (ARPES) is a key experimental technique for mapping the momentum-resolved electronic structure of crystalline materials. Combining the pump-probe scheme with ARPES allows to extend this technique to the time-domain and to probe excited states of materials [1].

In this presentation, I will showcase some powerful capabilities of time-resolved ARPES. I will exemplify how it can be used to map the unoccupied states of crystalline materials, with the case of the semiconductor WSe₂ [2]. Time-resolved techniques have been frequently used in the last decade for studying photoinduced phase transitions, and possibly generating novel out-of-equilibrium states. In that perspective, I will discuss the case of the layered material Ta₂NiSe₅ that has been proposed as an excitonic insulator phase [3]. I will also illustrate how a transient enhancement of ferroelectricity can be generated in the Rashba semiconductor GeTe [4].

[1] F. Boschini et al., Rev. Mod. Phys.  96, 1 (2024).
[2] M. Puppin et al., Phys. Rev. B 105, 075417 (2022).
[3] S. Mor et al., Phys. Rev. Lett. 119, 086401 (2017).
[4] G. Kremer et al., Nature Comm. 13, 6396 (2022).