Berlin 2024 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 20: Poster I

MA 20.19: Poster

Dienstag, 19. März 2024, 16:30–19:00, Poster A

THz spin and charge currents in a non-centrosymmetric ferromagnet — Junwei Tong¹, Zdenek Kaspar¹, Afnan Alostaz^1,5, Bruno Serrano¹, Xianmin Zhang², Genaro Bierhance^1,4, F. Gerhard³, Johannes Kleinlein³, Tobias Kießling³, Charles Gould³, Laurens Molenkamp³, Tom Seifert¹, and •Tobias Kampfrath^1,4 — ¹Freie Universität Berlin, Germany — ²Northeastern University, China — ³Physikalisches Institut der Universität Würzburg (EP3), and Institute for Topological Insulators, Am Hubland, Germany — ⁴Fritz Haber Institute of the Max Planck Society, Germany — ⁵Jülich Research Center, Germany

Investigating spin-to-charge conversion (SCC) on ultrafast time scales is important for understanding its physical mechanisms and the development of terahertz (THz) sources. SCC may arise from, e.g., the inverse spin Hall effect and spin-galvanic effect, whose experimental separation is challenging. Here, we use a femtosecond laser pulse to excite thin films of the ferromagnetic Heusler compound NiMnSb and measure the emitted THz electromagnetic pulse. We observe THz signals and, thus, ultrafast photocurrents that can be ascribed to SCC by contributions with Rashba- and Dresselhaus-like symmetry. Based on a symmetry analysis, we separate both contributions and find that the related photocurrents exhibit different temporal dynamics. Further, by changing the magnetic field, we observe that the Rashba-like current is mainly induced by ordinary Hall effect, whereas the Dresselhaus-like current is independent of the magnetic field strength. We discuss possible microscopic scenarios of the Dresselhaus-like contribution.

Keywords: Spin-to-charge conversion; Terahertz; Dresselhaus effect; Rashba effect