1 Swiss Light Source, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland
2 Deutsches Elektronen-Synchrotron DESY, Notkestraße 85, 22607, Hamburg, Germany
3 SwissFEL, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland
4 Laboratoire de Spectroscopie Ultrarapide (LSU) and Lausanne Centre for Ultrafast Science (LACUS), Ecole Polytechnique Fédérale de Lausanne (EPFL), ISIC-FSB, Station 6, 1015 Lausanne, Switzerland
5 Laboratory for Multiscale Materials Experiments, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland
6 Laboratory for Mesoscopic Systems, Department of Materials, ETH Zürich, 8093 Zürich, Switzerland
7 Institute for Quantum Electronics, ETH Zürich, 8093 Zürich, Switzerland.
8 Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland
9 Department of Physics, Kyushu University, Fukuoka 819-0395, Japan
10 Institute for Solid State Physics, University of Tokyo, Chiba 277-8581, Japan.
11 Department of Physics, University of Tokyo, Tokyo 113-0033, Japan.
12 Graduate School of Material Science, University of Hyogo, 3-2-1, Koto, Kamigori-cho, Ako-gun, Hyogo 678-1297, Japan
* Corresponding authors emails:
How to cite this record
Ultrafast electron localization in the EuNi2(Si0.21Ge0.79)2 correlated metal
, Materials Cloud Archive
Ultrafast electron delocalization induced by a femtosecond laser pulse is a well-known process in which electrons are ejected from the ions within the laser pulse duration. However, very little is known about the speed of electron localization out of an electron gas in correlated metals, i.e., the capture of an electron by an ion. Here, we demonstrate by means of pump-probe x-ray techniques across the Eu L3 absorption edge that an electron localization process in the EuNi2(Si0.21Ge0.79)2 intermetallic material occurs within a few hundred femtoseconds after the optical excitation. Spectroscopy and diffraction data collected simultaneously at low temperature and for various laser fluences show that the localization dynamics process is much faster than the thermal expansion of the unit cell along the c direction which occurs within picoseconds. Nevertheless, this latter process is still much slower than pure electronic effects, such as screening, and the subpicosecond timescale indicates an optical phonon drive origin. In addition, comparing the laser fluence dependence of the electronic response with that found in other intermediate 4 f valence materials, we suggest that the electron localization process observed in this Eu-based correlated metal is mainly related to changes in the 4 f hybridization. The observed ultrafast electron localization process sparks fundamental questions for our understanding of electron correlations and their coupling to the lattice.
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Ultrafast electron delocalization
pump and probe x-ray techniques