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Theme 3 colloquium: "Terahertz Photonics for Ultrafast Magnetism" (Lecture)

Date
Tuesday 19 September 2017Add to my calendar
Time
from 16:00
Location
HG00.303
Speaker
Dr. Rostislav Mikhaylovskiy, Spectroscopy of Solids and Interfaces
Description

rostislavTerahertz (THz) electro-magnetic radiation has a direct access to electron spins in solids. As the meV photon energy at THz frequencies matches the energy scale of the magnetic exchange and spin-orbit interactions, the terahertz waves can probe and control ultrafast magnetization dynamics. Yet, until recently potential of THz radiation has not been utilized in the field of magnetism.

In my talk I will explain how THz emission spectroscopy can be applied as an ultrafast magnetometer allowing to trace picosecond spin dynamics and a femtosecond amperemeter for spin-polarized currents. These developments allowed us to discover light-induced modification of the exchange interaction in a broad class of antiferromagnetic oxides [1] and generation of spin-polarized photo-currents at interfaces of metallic magnetic heterostructures [2].

In the second part of my talk I will discuss the potential of intense THz-radiation to control spins in magnetic materials. An efficient mechanism for such a control based on interplay between rare-earth orbitals and transition metal spins in antiferromagnetic insulators will be suggested [3]. Particularly, by resonant pumping low-energy rare-earth orbitals one can manipulate magnetic anisotropy, which in turn can efficiently drive spin motion in nonlinear regime [4]. The strength of the THz-driven anisotropy torque can exceed the Zeeman torque exerted by the magnetic field by at least one order of magnitude. By further increasing the anisotropy torque with the help of plasmonic THz antennas, in our latest measurements we indicate that the THz-driven magnetization switching can be indeed achieved in the experiment. In this way the magnetic recording at THz clock rates is made feasible.

Finally, I will draw future directions for terahertz photonics in the area of ultrafast spin dynamics, such as selective excitation and coherent control with free electron lasers, magnon-polaritonics and THz 2-dimensional spectroscopy of magnetic kinetics.

[1]. R. V. Mikhaylovskiy, et al. Ultrafast optical modification of exchange interactions in iron oxides. Nature Communications 6, 8190 (2015).

[2]. T. J. Huisman, R. V. Mikhaylovskiy, et al. Femtosecond control of electric currents in metallic ferromagnetic heterostructures. Nature Nanotechnology 11, 455 (2016).

[3]. R. V. Mikhaylovskiy, et al. Selective excitation of terahertz magnetic and electric dipoles in Er3+ ions by femtosecond laser pulses in ErFeO3. Phys. Rev. Lett. 118, 017205 (2017).

[4]. S. Baierl, M. Hohenleutner, T. Kampfrath, A. K. Zvezdin, A. V. Kimel, R. Huber, and R. V. Mikhaylovskiy. Nonlinear spin control by terahertz driven anisotropy fields. Nature Photonics 10, 715 (2016).