Berlin 2024 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 34: Focus Session: Dynamical Probes for Topological Magnetism

TT 34.1: Hauptvortrag

Mittwoch, 20. März 2024, 09:30–10:00, H 0104

A phononic route to ultrafast control of magnetic order — •Andrei Kirilyuk — FELIX Laboratory, Radboud University, 6525 ED Nijmegen, The Netherlands

Strong light-matter interaction constitutes the basis of all photonic applications, empowering material elements to create and mediate interactions of light with light. Among others, phonon-amplified interactions were shown to bring a specific twist into this. In this case, light couples to the spins indirectly by exciting coherent vibrations of the crystal lattice (phonons) that transfer angular momentum to the magnetic ions. The optically driven chiral phonons were shown to possibly produce giant effective magnetic fields. The mechanism allows for bidirectional control of the induced magnetisation through phonon chirality that in turn can be controlled by the polarisation of the laser pulse.

Here we show that through the resonant excitation of circularly-polarized optical phonons in paramagnetic substrates, one can permanently reverse the magnetic state of the substrate-mounted heterostructure. With the handedness of the phonons steering the direction of magnetic switching, such effect offers a selective and potentially universal method for ultrafast non-local control over magnetic order.

Moreover, a different behavior, characterized by displacive modification of magnetic potentials, can be observed when exciting materials at phonon frequencies with linearly-polarized light. The magnetic switching was shown to create very peculiar patterns, confirming the mechanism.

Keywords: Ultrafast magnetization dynamics; Spin-phonon coupling