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seminar by dr. Dmytro Afanasiev: 'Light-driven phonomagnetism' (Lecture)

Date
Friday 26 March 2021Add to my calendar
Time
from 16:00
Location
zoom
Speaker
dr. Dmytro Afanasiev (Univ. Regensburg, Germany)
Description

Resonant pumping of infrared-active phonons with light pulses in the mid-infrared spectral (MIR) range has emerged as a low-energy route to drive large-amplitude coherent net structural distortions. These distortions, emerging on the timescale of several picoseconds, modulate the spatial overlap of the electronic wave functions and have been shown to transiently melt charge and orbital ordering, drive metal-insulator phase transitions and even enhance superconducting correlations in high-TC cuprates(1). Although pioneering experiments have demonstrated that driving optical phonons can also impact magnetism, no coherent switching of the spin orientation or coherent light-induced magnetic symmetry breaking has been shown until very recent(2, 3).

In this presentation I will outline possible strategies to control magnetism using resonant pumping of infrared active phonons and present our latest experimental results on phonon-induced magnetism (phonomagnetism) in dysprosium orthoferrite (DyFeO3). DyFeO3 an antiferromagnetic oxide where a strong exchange interaction between the spin of the transition metal ion (Fe) and the orbital momentum of the rare-earth ion (Dy) leads to a distinctive first-order spin-reorientation phase transition accompanied by a change of the magnetic symmetry from the antiferromagnetic (AFM) to the weakly ferromagnetic (WFM). We show that a sub-ps pulse of an intense multi-THz electric field, tuned to resonance with a phonon mode, drives a coherent spin-reorientation, developing long-living net magnetic moment within a half-cycle of the spin precession. Phonon-induced magnetism emerges via a non-equilibrium metastable state, inaccessible not only via a thermodynamic transformation but also via optical pumping of the high-energy electronic transitions. We experimentally and theoretically demonstrate that phonomagnetism originates from phonon-induced lattice distortions leading to ultrafast modification of the RE-TM exchange interaction.

  1. R. Mankowsky, M. Först, A. Cavalleri, Non-equilibrium control of complex solids by nonlinear phononics. Reports on Progress in Physics79, 064503 (2016).
  2. A. Stupakiewicz et al., Ultrafast phononic switching of magnetization. Nature Physics, 1-4 (2021).
  3. D. Afanasiev et al., Ultrafast control of magnetic interactions via light-driven phonons. Nature Materials, 1-5 (2021).
Contact
prof. A. Kirilyuk
Register

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