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Phys. Rev. Lett. 128, 157205 (2022)

Light-Induced Magnetization at the Nanoscale

Jonas Wätzel1, Primož Rebernik Ribič2, Marcello Coreno2,3, Miltcho B. Danailov2, Christian David4, Alexander Demidovich2, Michele Di Fraia2, Luca Giannessi2,5, Klavs Hansen6, Špela Krušič7, Michele Manfredda2, Michael Meyer8, Andrej Mihelič7, Najmeh Mirian2,9, Oksana Plekan2, Barbara Ressel10, Benedikt Rösner4, Alberto Simoncig2, Simone Spampinati2, Matija Stupar10, Matjaž Žitnik7, Marco Zangrando2,11, Carlo Callegari2, Jamal Berakdar1 and Giovanni De Ninno2,10,*

1 Institut für Physik, Martin-Luther-Universität Halle-Wittenberg, 06099 Halle (Saale), Germany

2 Elettra-Sincrotrone Trieste S.C.p.A., 34149 Trieste, Italy

3 ISM-CNR, in Basovizza Area Science Park, 34149 Trieste, Italy

4 Paul Scherrer Institut, 5232 Villigen-PSI, Switzerland

5 INFN-LNF, Via E. Fermi 40, 00044 Frascati (Rome), Italy

6 Center for Joint Quantum Studies and Department of Physics, School of Science, Tianjin University, 300072 Tianjin, China

7 J. Stefan Institute, Jamova cesta 39, 1000 Ljubljana, Slovenia

8 European XFEL, Holzkoppel 4, 22869 Schenefeld, Germany

9 Deutsches Elektronen-Synchrotron (DESY), 22607 Hamburg, Germany

10 University of Nova Gorica, 5000 Nova Gorica, Slovenia

11 Istituto Officina dei Materiali, Consiglio Nazionale delle Ricerche, 34149 Trieste, Italy

Abstract

Triggering and switching magnetic moments is of key importance for applications ranging from spintronics to quantum information. A noninvasive ultrafast control at the nanoscale is, however, an open challenge. Here, we propose a novel laser-based scheme for generating atomic-scale charge current loops within femtoseconds. The associated orbital magnetic moments remain ferromagnetically aligned after the laser pulses have ceased and are localized within an area that is tunable via laser parameters and can be chosen to be well below the diffraction limit of the driving laser field. The scheme relies on tuning the phase, polarization, and intensities of two copropagating Gaussian and vortex laser pulses, allowing us to control the spatial extent, direction, and strength of the atomic-scale charge current loops induced in the irradiated sample upon photon absorption. In the experiment we used He atoms driven by an ultraviolet and infrared vortex-beam laser pulses to generate current-carrying Rydberg states and test for the generated magnetic moments via dichroic effects in photoemission. Ab initio quantum dynamic simulations and analysis confirm the proposed scenario and provide a quantitative estimate of the generated local moments.

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