Femtosecond light-induced phase transitions between different macroscopic orders provide the possibility to tune the functional properties of condensed matter on ultrafast timescales. In first-order phase transitions, transient non-equilibrium phases and inherent phase coexistence often preclude non-ambiguous detection of transition precursors and their temporal onset. Here, we present a study combining time-resolved photoelectron spectroscopy and ab-initio electron dynamics calculations elucidating the transient subpicosecond processes governing the photoinduced generation of ferromagnetic order in antiferromagnetic FeRh. The transient photoemission spectra are accounted for by assuming that not only the occupation of electronic states is modified during the photoexcitation process. Instead, the photo-generated non-thermal distribution of electrons modifies the electronic band structure. The ferromagnetic phase of FeRh, characterized by a minority band near the Fermi energy, is established 350 ± 30 fs after the laser excitation. Ab-initio calculations indicate that the phase transition is initiated by a photoinduced Rh-to-Fe charge transfer.

CEITEC BUT Brno University of Technology Brno Czech Republic

Deutsches Elektronen Synchrotron DESY Hamburg Germany

European Theoretical Spectroscopy Facility

Institute of Physical Engineering Brno University of Technology Brno Czech Republic

Istituto di Struttura della Materia Consiglio Nazionale delle Ricerche Monterotondo Stazione Italy

Johannes Gutenberg Universität Institute of Physics Mainz Germany

LSI CNRS CEA DRF IRAMIS École Polytechnique Institut Polytechnique de Paris Palaiseau France

Physique de la Matiére Condensée CNRS and École Polytechnique IP Paris Palaiseau France

Synchrotron SOLEIL L'Orme des Merisiers Gif sur Yvette France

The Hamburg Centre for Ultrafast Imaging Hamburg University Hamburg Germany

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Nat Commun. 2023 May 3;14(1):2545. doi: 10.1038/s41467-023-38263-5. PubMed

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