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Double seminar: 'Photonic wheels and magnetic field induced directional emission of excitons' and 'Ultrafast control of magnetic metastability using light-driven phonons' (Lecture)

Date
Monday 2 December 2019Add to my calendar
Time
from 14:00
Location
HG 00.616
Speaker
Prof.dr. Ilya Akimov (Technical University Dortmund) and Dr. Dmytro Afanasiev (Delft University of Technology)
Description

Double seminar preceding the PhD defense of the manuscript: “Ultrafast laser-induced spin dynamics beyond the three temperature model” by Anna Gatilova.

14.00 – 14.30     Prof.dr. Ilya Akimov (Technical University Dortmund), title: "Photonic wheels and magnetic field induced directional emission of excitons".

Abstract:
Photonic wheels carry transverse spin which is locked to the propagation direction of electromagnetic waves. Therefore, photonic wheels are attractive for spin manipulation and read-out in magnetic media. Emission effects are of particular interest. Here I will discuss a new class of emission phenomena where directionality is established perpendicular to the externally applied magnetic field for light sources located in the vicinity of a surface. As a proof of principle for this effect, which we call transverse magnetic routing of light emission, we demonstrate the routing of emission for excitons in a diluted-magnetic-semiconductor quantum well. In hybrid plasmonic semiconductor structures, we observe significantly enhanced directionality of up to 60%.

14.30 – 15.00    Dr. Dmytro Afanasiev (Delft University of Technology), title: “Ultrafast control of magnetic metastability using light-driven phonons”.

Abstract:
Over the past few decades, ultrashort pulses of light have been widely employed to control the behaviour of matter in its different phases. This is a particularly interesting challenge in magnetism, where the speed, dissipation and routes for ultimately fast switching of the spin orientation often lead to proposals for novel approaches in information processing and data recording.  [1]

Artistic representation of the effect from optically-driven phonons on the profile of the magnetic energyFigure 1. Artistic representation of the effect from optically-driven phonons on the profile of the magnetic energy

In this work we control the magnetic state by resonantly pumping optical phonons, low-energy elementary vibrations of the crystalline lattice. We demonstrate that by exciting the crystal lattice of the prototypical antiferromagnetic DyFeO3, it can be driven within picoseconds into a transient metastable magnetic state. The state is characterized by a change in the strength of magnetic anisotropy along different crystal axes. This is experimentally seen as a long-lived shift in the frequency of the spin precession driven along the corresponding axes. For sufficiently strong excitation, this promotes an instability of the initial magnetic structure and launches a spin reorientation transition within a few picoseconds.

[1] P. Němec et al., Nature Physics 14, 229 (2018).

16.30     Defense Anna Gatilova

Contact
prof. Theo Rasing & prof. Alexey Kimel