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MA: Fachverband Magnetismus

MA 24: Terahertz Spintronics I

MA 24.2: Vortrag

Mittwoch, 20. März 2024, 09:45–10:00, EB 202

Accessing ultrafast spin-transport dynamics in copper using broadband terahertz spectroscopy — •Reza Rouzegar^1,3, Jiri Jechumtal², Oliver Gueckstock^1,3, Wolfgang Hoppe⁵, Quentin Remy¹, Tom Seifert¹, Georg Woltersdorf⁵, Piet Brouwer¹, Markus Münzenberg⁴, Tobias Kampfrath¹, and Lukas Nadvornik² — ¹Freie Universität Berlin — ²Charles University, Prague — ³Fritz-Haber-Institute, Berlin — ⁴Universität Greifswald — ⁵Martin-Luther-Universität Halle

We study femtosecond spin currents through Cu in CoFeB(2 nm)|Cu(d)| Pt(2 nm) stacks by terahertz emission spectroscopy. In our approach, spin currents are transmitted through a Cu(d) interlayer with thickness d and converted into a measurable charge current in Pt. The spin current j_s^d(t) vs time t behind the Cu layer exhibits an increasing delay and stronger dispersion when d increases [1]. Using an analytical dynamic-diffusion model, we can describe the spin current propagation for a spin velocity of 1.1 nm/fs, which agrees well with the Fermi velocity of Cu, and an electron scattering time of τ=4 ± 2 fs. In the framework of our model, we can separate ballistic and diffusive components of the spin current [1]. We conclude that, for thicknesses of d≥ 2 nm, the spin current is dominated by diffusive transport.

[1] J. Jechumtal, R. Rouzegar, et.al., arXiv:2310.12082 (2023).

Keywords: Spin transport; Diffusive and ballistic transport; Terahertz spectroscopy