2024/06/17(Mon) 10:30 -11:30 五樓第一會議室 5F, 1st Meeting Room
Title
Coherent terahertz electric field drive of Weyl semimetal Co2Sn2S2
Speaker
渡邊浩助理教授 (大阪大學) Assistant Professor Hiroshi Watanabe (Graduate School of Frontier Biosciences Osaka University)Abstract
The coherent electric field drive by photoelectric fields have been attracted in recent years [1,2]. However, it has been very difficult to observe photoelectric field-driven phenomena in solids because the electron scattering time of ordinary materials is very fast, on the order of 10 fs, and electron scattering disturbs the coherence between light and electrons. Therefore, we have attempted to observe photoelectric field driven phenomena in the THz frequency band (~1 ps) by using Weyl semimetals, which have relatively long electron scattering times (several hundred fs to several ps).
We have measured the excitation intensity dependence of the high power THz pump/THz reflection spectra in the ferromagnetic Wely semimetal Co3Sn2S2 with a Weyl band of a few ten meV at 7 K. High power THz pulses were generated by Ti-sapphire laser (1.55 eV, 1 mJ, 1 kHz, 70 fs) in a LiNO3 crystal using the tilted wave front method. Figures 1 (a), (b), and (c) show the field intensity dependences of THz electric field waveform, the Fourier spectrum, and the intensity at 0.2 and 0.8 THz, independently. As shown in Fig. 1(b), a peak structure centered at 0.8 THz and a broad structure around 0.2 THz appeared, and the broad structure at 0.2 THz shows a nonlinear process proportional to the square of the excitation intensity as shown in Fig. 1(c). This indicates a DC current due to the coherent acceleration by the THz electric field and the non-adiabatic excitation process.
[1] T. Higuchi, et al., Nature 550, 224–228 (2017).
[2] Y. Kawakami, et al., Nat. Commun. 11, 4138 (2020).
Abstract
Language
演講語言 (Language): in English
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