학술논문
Terahertz Spin‐to‐Charge Current Conversion in Stacks of Ferromagnets and the Transition‐Metal Dichalcogenide NbSe2
Document Type
article
Author
Lukáš Nádvorník; Oliver Gueckstock; Lukas Braun; Chengwang Niu; Joachim Gräfe; Gunther Richter; Gisela Schütz; Hidenori Takagi; Mahmoud Zeer; Tom S. Seifert; Peter Kubaščík; Avanindra K. Pandeya; Abdelmadjid Anane; Heejun Yang; Amilcar Bedoya‐Pinto; Stuart S. P. Parkin; Martin Wolf; Yuriy Mokrousov; Hiroyuki Nakamura; Tobias Kampfrath
Source
Advanced Materials Interfaces, Vol 9, Iss 36, Pp n/a-n/a (2022)
Subject
Language
English
ISSN
2196-7350
Abstract
Abstract Transition‐metal dichalcogenides (TMDCs) are an aspiring class of materials with unique electronic and optical properties and potential applications in spin‐based electronics. Here, terahertz emission spectroscopy is used to study spin‐to‐charge current conversion (S2C) in the TMDC NbSe2 in ultra‐high‐vacuum‐grown F|NbSe2 thin‐film stacks, where F is a layer of ferromagnetic Fe or Ni. Ultrafast laser excitation triggers an ultrafast spin current that is converted into an in‐plane charge current and, thus, a measurable THz electromagnetic pulse. The THz signal amplitude as a function of the NbSe2 thickness shows that the measured signals are fully consistent with an ultrafast optically driven injection of an in‐plane‐polarized spin current into NbSe2. Modeling of the spin‐current dynamics reveals that a sizable fraction of the total S2C originates from the bulk of NbSe2 with the opposite, negative sign of the spin Hall angle as compared to Pt. By a quantitative comparison of the emitted THz radiation from F|NbSe2 to F|Pt reference samples and the results of ab initio calculations, it is estimated that the spin Hall angle of NbSe2 for an in‐plane polarized spin current lies between ‐0.2% and ‐1.1%, while the THz spin‐current relaxation length is of the order of a few nanometers.