Abstract-High performance terahertz emitter based on inverse spin Hall effect in metallic Fe/Au heterostructure

Omid Panahi, Bahareh Yahyaei, Seyed Mahdi Mousavi,  Aboozar Masoomi Ghiasabadi, 



https://iopscience.iop.org/article/10.1088/1555-6611/ab7dd0

Since many applications of terahertz spectroscopy depend on spectral bandwidth, the generation of ultra-broadband terahertz radiation is one of the most important challenges faced by terahertz scientists. Spintronic terahertz emitters (STEs) are promising sources to produce very compact terahertz pulses and broadband spectra. Here we optimized the iron/gold heterostructure based on the metal layer thicknesses for the first time. The optimization was performed experimentally based on the obtained theoretical results. The optimized thicknesses were obtained as 2 and 5 nm for Fe and Au layers, respectively. The experimental results were in very good agreement with corresponding theoretical results. The optimized STE generates terahertz bandwidth up to 4 THz which is limited by the frequency response of the used detector. The dynamic range is well above 60 dB with the maximum around 0.5 THz. The results show that the presented STE is capable of producing large amplitude terahertz pulses and broadband spectral range. Based on our knowledge, this is the first time that the Fe/Au spintronic terahertz emitter has been optimized.

Abstract-Complex THz and DC inverse spin Hall effect in YIG/Cu1-xIrx bilayers across a wide concentration range

Joel Cramer, Tom Seifert, Alexander Kronenberg, Felix Fuhrmann, Gerhard Jakob, Martin Jourdan, Tobias Kampfrath, Mathias Kläui,

 https://www.blogger.com/blogger.g?blogID=124073320791841682#editor/target=post;postID=5107858870227750964

We measure the inverse spin Hall effect of Cu1-xIrx thin films on yttrium iron garnet over a wide range of Ir concentrations (0.05 ≦ x ≦ 0.7). Spin currents are triggered through the spin Seebeck effect, either by a DC temperature gradient or by ultrafast optical heating of the metal layer. The spin Hall current is detected by, respectively, electrical contacts or measurement of the emitted terahertz radiation. With both approaches, we reveal the same Ir concentration dependence that follows a novel complex, non-monotonous behavior as compared to previous studies. For small Ir concentrations a signal minimum is observed, while a pronounced maximum appears near the equiatomic composition. We identify this behavior as originating from the interplay of different spin Hall mechanisms as well as a concentration-dependent variation of the integrated spin current density in Cu1-xIrx. The coinciding results obtained for DC and ultrafast stimuli provide further support that the spin Seebeck effect extends to terahertz frequencies, thus enabling a transfer of established spintronic measurement schemes into the terahertz regime. Our findings also show that the studied material allows for efficient spin-to-charge conversion even on ultrafast timescales.