Ultrafast electron localization in the EuNi2(Si0.21Ge0.79)2 correlated metal

Jose R.L. Mardegan, Serhane Zerdane, Giulia Mancini, Vincent Esposito, Jérémy R. Rouxel, Roman Mankowsky, Cristian Svetina, Namrata Gurung, Sergii Parchenko, Michael Porer, Bulat Burganov, Yunpei Deng, Paul Beaud, Gerhard Ingold, Bill Pedrini, Christopher Arrell, Christian Erny, Andreas Dax, Henrik Lemke, Martin DeckerNazaret Ortiz, Chris Milne, Grigory Smolentsev, Laura Maurel, Steven L. Johnson, Akihiro Mitsuda, Hirofumi Wada, Yuichi Yokoyama, Hiroki Wadati, Urs Staub

Research output: Contribution to journalArticlepeer-review

3 Citations (Scopus)


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 driven origin. In addition, comparing the laser fluence dependence of the electronic response with that found in other intermediate 4f valence materials, we suggest that the electron localization process observed in this Eu-based correlated metal is mainly related to changes in the 4f hybridization. The observed ultrafast electron localization process sparks fundamental questions for our understanding of electron correlations and their coupling to the lattice.

Original languageEnglish
Article number033211
JournalPhysical Review Research
Issue number3
Publication statusPublished - Sept 2021

All Science Journal Classification (ASJC) codes

  • General Physics and Astronomy


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