Recent Advances in Probing Excited States of Solids by Time-resolved ARPES

by Prof. Martin Wolf (Fritz Haber Institute, Physical Chemistry, Max Planck Society, Berlin)

Tuesday 13 Apr 2021, 13:00 → 14:00 Europe/Berlin

Zoom meeting

Interaction of many-body systems with ultrashort light pulses may lead to emergent phenomena away from equilibrium like photo-stabilization of hidden phases or ultrafast phase transitions. These processes are characterized by pronounced chan­ges in the electronic structure and occupation of electronic states. Recent advances in ultrafast spectro­scopy allow direct probing of the underlying fundamental steps and provide a mechanistic understanding of transfer of energy from the electronic system into nuclear motions.

Here I will discuss recent advances to probe such transient changes by a table-top 500 kHz HHG based XUV laser source enabling excited state band mapping throughout the complete Brillouin zone by time-resolved photoemission spectroscopy (trARPES) [1]. Within the same setup we have implement a hemispherical analyzer and a momentum microscope and we highlight the advantages and limitations of both instruments based on exemplary trARPES measurements of bulk WSe2, depending on pump- and probe-induced space-charge effects, detection efficiency, photoelectron count rates [2]. Such trARPES experiments provide detailed insights into the photo-induced phase transition in quasi-1D metal nanowires on In/Si(111) [3], the ultrafast Lifshitz transition in MoTe2 [4], non-equilibrium CDW dynamics in TbTe3 [5] and the spatial extend of the excitonic wave function in WSe2 [6], which will be discussed as examples.

[1] M. Puppin et al., Rev. Sci. Instr. 90, 023104 (2019)

[2] J. Makler et al., Rev. Sci. Instr. 91, 123112 (2020) 

[3] C.W. Nicholson et al., Science 362, 821 (2018)

[4] S. Beaulieu et al., Science Advances (accepted, arXiv:2003.04059)

[5] J. Makler et al., Nature Communications (accepted, arXiv:2011.03230)

[6] S. Dong et al., arXiv:2012.15328

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