Terahertz Spectroscopy of Ultrafast Spin Dynamics | Dr. Rostislav Mikhaylovskiy

Описание: Timecodes are below the Title.

Dr. Rostislav Mikhaylovskiy,
Lancaster University

Title: "Terahertz Spectroscopy of Ultrafast Spin Dynamics"

00:00:04 Speaker introduction
00:01:17 Start of the talk
00:01:44 Acknowledgements
00:02:17 Outline of the talk
00:03:04 How fast is magnetism
00:06:32 Ultrafast magnetism - new physics
00:07:35 Why terahertz spectroscopy
00:09:47 Elusive boundary between optics and magnetics
00:16:27 Our aproach: terahertz spectroscopy
00:18:09 Terahertz emission from Co film
00:21:15 THz look at processes during laser excitation. Photo spinn currents
00:21:26 THz emission from bilayers
00:24:31 Symmetry: magnetization odd
00:26:19 Ultrafast spin galvanic effect
00:26:19 THz look at processes during laser excitation. Exchange modulation
00:30:50 THz emission from iron oxides
00:40:40 Beyond optical excitation
00:41:45 THz control of the spins
00:42:48 Electric field driven THz control
00:45:06 Spin reorientation in TmFeO3
00:46:54 Terahertz-driven spin reorientation
00:47:28 THz-pump optical probe experiment
00:48:15 TmFeO3: antiferromagnetic resonance
00:51:30 THz-spin nonlinearity in TmFeO3
00:52:50 Origin of nonlinearity?
00:52:57 Phenomenology of nonlinearity
00:56:12 THz excitations in TmFeO3
00:56:50 Spectral filtering
00:57:41 Terahertz-driven anisotropy change
00:58:27 THz-driven anisotropy in DyFeO3
00:59:04 Towards THz-switching
01:01:18 Near-field THz control of spins
01:03:58 Strongly non-linear spin response
01:05:41 Origin of the nonlinearity
01:08:25 Fingerprint of all-coherent switching
01:08:58 Electric-driven terahertz control
01:09:50 Summary
01:10:20 Discussion

Abstract: Terahertz (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.

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