An excited electron in condensed matter propagates with its momentum
k at an energy E k ) and experiences
elastic and inelastic scattering processes, which lead to relaxation. Experiments employing f emtosecond
time resolved photoelectron spectroscopy exploited so far very successfully the surface sensitivity of photo
electron spectroscopy and probed such scattering processes locally at the surface or the surface near region in the
time domain [1]. Here, we report on experimental results which analyze the non local dynamics of excited
electrons propagating through laye r stacks using two photon photo electron emission spectroscopy (2PPE). In
these experiments one photon excites in a Au/Fe/MgO(001) heterostructure electrons in Fe. Electron propagation
th rough the layer stack to the Au surface is detected in 2PPE in back pump front probe experiments 2 ]], similar
to pioneering femtosecond pump probe experiments in condensed matter, which revealed time dependent
changes in the linear optical reflectivity of free standing Au films [ 3 We observe pronounced differences
between front and back pumping the hetero structure which are attribu ted to superdiffusive electron transport 4 ]
contributions through the layer stack Furthermore, we investigate the relaxation of electronic excitation s in the
charge density wave / Mott system 1 T TaS 2 with femtosecond photoelectron sp ectroscop y 5 ,6 ]]. In such Mott
systems double electron popu lation of single sites represe nt doublo n e xcitatio ns and the u ltrafast doublon
dynamics including scattering of Bloch electrons with doublon excitations will be discus sed
This work was funded by the Deu
tsche Forschungsgemeinschaft through the Collaborative Research Center
CRC 1242 (project number 278162697)
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5 M. Ligges, I. Avigo, D. Golez, H. U. R. Strand, Y. Beyazit, K. Hanff, F. Diekmann, L. Stojchevska, M.
Kalläne, K. Rossnagel, M. Eckstein, P. Werner, U. Bovensiepen, Phys. Rev. Lett. 120 , 166401 2018
[
6 I. Avigo, F. Queisser, P. Zhou, M. Ligges, K. Rossnagel, R. Schützhold, U. Bovensiepen,
Phys. Rev. Research 2 , 0 2 2 04 6 R 20 20