IRP13
Location
Palaiseau, France
Host institution
THALES is a world leader group for electronics and a key player in numerous markets (defence, security, space, aerospace and ground transportation) with 8000 employees in 56 different countries. THALES performs pioneering work in the most advanced areas of optics & optoelectronics, lasers, electronic components for microwave applications, spintronics, superconductive materials and devices, carbon nanotubes and graphene devices, packaging, materials, software architecture and cognitive science.
Supervisor
Dr. Romain Lebrun
Description
Objectives: Research in spintronics has recently shown a great potential towards the development of spin-based GHz and THz devices [1]. Recent developments have shown the possibility to generate, manipulate and control not only spin but orbital angular momentum in solids, at various time scales [2]. This experimental project aims at unraveling the orbital-to-charge interconversion processes in active spintronic hetero-structures (including standard ferromagnetic materials [1], as well as antiferromagnetic materials [3]) using mainly optical THz time domain spectroscopy, as well potentially electrical GHz Vector Network Analyzer spectroscopy.
To investigate spin and orbital-current dynamics at femtosecond times, one can employ femtosecond pulse (10-100 fs) as an optical pump to excite thin metallic magnetic layer, (or potentially ferromagnetic and antiferromagnetic insulators [3]) and subsequently generate ultra-short orbital or spin-current. This current source relaxes at the interface with an active material (like Ti, Cu/CuOx via orbital Hall effect, or Pt, W or Ta heavy metals via inverse spin-Hall effect), leading to the generation of charge dipole oscillators in the sub-picosecond range and the emission of short THz radiation wave. Using electro-optical sampling, one can access to the following allows:
- the determination fo the physical parameters determining the typical electron and orbital/spin relaxation processes at the interfaces or in the bulk materials at their vicinity,
- determining the specific electronic interactions at these interfaces and
- the electron-light coupling allowing the emission in the THz range.
Alternatively, orbital current can be used to manipulate the magnetic state and magnetization dynamics via orbital torques, which is anticipated to enable the development of more frugal spintronic and magnonic devices [4].
In this IRP, the first goal is to explore orbital current to magnon interconversion mediated by spin-orbit coupling in conventional bilayers of low damping ferromagets (doped YIG, CoFeB) and heavy metal with an extra-capping of light materials with large orbital Hall effect (OHE). The successful candidate will also investigate direct orbital current to magnonic excitation in magnetic materials with magnons carrying intrinsically orbital angular momentum. To unravel the OHEs on the THz magnon modes in most of these compounds, the PhD student will perform THz time domain spectroscopy at the host organization combined. Thirdly, we will investigate by time-resolved transport measurements (iii) how orbital torques can trigger complex magnetization dynamics of 3D spin-textures, that can also host magnon mode carrying orbital angular momentum. In the end, we will target to model by semi-phenomenological numerical techniques the correlated response at the femtosecond scale between the dynamics of the magnonic spin-current giving rise to the THz emission and the dynamics of the orbital angular momentum.
[1] T. H. Dang et al., Ultrafast spin-currents and charge conversion at 3d-5d interfaces probed by time-domain terahertz spectroscopy, Applied Physics Reviews 7, 041409 (2020).
[2] T. S. Seifert, D. Go, H. Hayashi, R. Rouzegar, F. Freimuth, K. Ando, Y. Mokrousov, and T. Kampfrath, Time-domain observation of ballistic orbital-angular-momentum currents with giant relaxation length in tungsten, Nat. Nanotechnol. 1 (2023).
[3] E. Rongione et al., Emission of coherent THz magnons in an antiferromagnetic insulator triggered by ultrafast spin–phonon interactions, Nat Commun 14, 1 (2023).
[4] H. Merbouche, B. Divinskiy, D. Gouéré, R. Lebrun, A. El Kanj, V. Cros, P. Bortolotti, A. Anane, S. O. Demokritov, and V. E. Demidov, True amplification of spin waves in magnonic nano-waveguides, Nat Commun 15, 1560 (2024)
Requirements
Master’s degree in physics, optics, condensed matter or nanotechnologies
Planned Secondments
- Academic secondment at Johannes Gutenberg Universität, under the supervision of Yuriy Mokrousov,
- Academic secondment at Freie Universität Berlin, under the supervision of Tom Seifert
Planned Secondments
Academic Secondment
ohannes Gutenberg Universität
Mainz, Germany
Yuriy Mokrousov
Academic Secondment
Freie Universität Berlin
Berlin, Germany
Tom Seifert
Registering University
Université Paris-Saclay
