Quasi-two-dimensional van der Waals ferromagnetic semiconductor CrGeTe3 studied by THz spectroscopy

doi:10.7498/aps.71.20221586

	Quasi-two-dimensional van der Waals ferromagnetic semiconductor CrGeTe3 studied by THz spectroscopy
	Wang Chen 1; Xia Wei2 ; Suo Peng 1; Wang Wei 1; Lin Xian 1; Guo Yan-Feng2,3 ; Ma Guo-Hong 1,3
	2022-12-05
发表期刊	ACTA PHYSICA SINICA
ISSN	1000-3290
卷号	71 期号:23
发表状态	已发表
DOI	10.7498/aps.71.20221586
摘要	The quasi-two-dimensional van der Waals intrinsic ferromagnetic semiconductor CrGeTe3 possesses both a narrow semiconductor band gap and ferromagnetic properties, which makes it have a broad application prospect in the fields of spintronics and optoelectronics. In recent years, CrGeTe3 has received extensive attention from researchers. To the best of our knowledge, so far, these studies have mainly focused on the optical response in near infrared and visible light range, but little has been done in THz frequency range. Therefore, it is upmost importance to obtain the complex dielectric constant as well as the photocarrier dynamics of the CrGeTe3 at the THz frequency. Herewith, we use time-domain THz spectroscopy and time-resolved THz spectroscopy to investigate the fundamental properties of the CrGeTe3 crystal in the THz range, including refractive index and absorption coefficient in THz frequency, as well as the THz photocarrier dynamics under 780-nm optical excitation. The fundamental characterizations are carried out on a 33-nm-thick CrGeTe3 wafer by Fourier infrared spectroscopy, X-ray diffraction and Raman scattering. It is concluded that the CrGeTe3 wafer shows an indirect band gap of 0.38 eV and good crystalline quality. The THz time domain spectroscopy presents that the CrGeTe3 wafer has a refractive index and an absorption coefficient of 3.2 and 380 cm(-1), respectively, both of which show almost negligible dispersion in the investigated THz frequency. Under the optical excitation of 780 nm, the subsequent photocarrier relaxation can be well reproduced by a double exponential function: the fast relaxation shows a lifetime of 1-2 ps, depending on pump fluence, which is contributed by electron-phonon coupling; the slow relaxation has a typical lifetime of 7-8 ps, which is due to phonon-assisted electron-phonon recombination. The Pump fluence and delay time dependence of THz photoconductivity dispersion can be well fitted with Drude-Smith model, and the fitted results demonstrate that the plasma frequency increases with pump fluence in a fixed delay time, and then decreases with delay time increasing at a fixed pump fluence. The momentum scattering time shows that it decreases with pump fluence increasing, and increases with delay time increasing. These pump fluence and delay time dependent fitting microscopic parameters show similar tendencies to those of a conventional semiconductor. In a word, the experimental study here demonstrates that the narrow band-gap CrGeTe3 wafer is well transparent and disperionless in a THz frequency range. From the above bandgap photoexcitation it follows that the wafer shows fast response and high modulation depth in THz radiation, providing a useful reference for the application of CrGeTe3 in optoelectronics and related fields.
关键词	van der Waals ferromagnetic semiconductor time-resolved spectroscopy terahertz spectroscopy
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收录类别	SCI ; 北大核心
语种	英语
资助项目	National Natural Science Foundation of China["92150101","61735010"] ; Science and Technology Innovation Action Program of the Shanghai Committee of Science and Technology, China[21JC1402600]
WOS研究方向	Physics
WOS类目	Physics, Multidisciplinary
WOS记录号	WOS:000898652500019
出版者	CHINESE PHYSICAL SOC
文献类型	期刊论文
条目标识符	https://kms.shanghaitech.edu.cn/handle/2MSLDSTB/268672
专题	物质科学与技术学院_公共科研平台_拓扑物理实验室物质科学与技术学院_PI研究组_郭艳峰组
通讯作者	Ma Guo-Hong
作者单位	1.Shanghai Univ, Dept Phys, Shanghai 200444, Peoples R China 2.Shanghai Tech Univ, Sch Phys Sci & Technol, Shanghai 201210, Peoples R China 3.STU&SIOM Joint Lab Superintense Lasers & Applicat, Shanghai 201210, Peoples R China
推荐引用方式 GB/T 7714	Wang Chen,Xia Wei,Suo Peng,et al. Quasi-two-dimensional van der Waals ferromagnetic semiconductor CrGeTe3 studied by THz spectroscopy[J]. ACTA PHYSICA SINICA,2022,71(23).
APA	Wang Chen.,Xia Wei.,Suo Peng.,Wang Wei.,Lin Xian.,...&Ma Guo-Hong.(2022).Quasi-two-dimensional van der Waals ferromagnetic semiconductor CrGeTe3 studied by THz spectroscopy.ACTA PHYSICA SINICA,71(23).
MLA	Wang Chen,et al."Quasi-two-dimensional van der Waals ferromagnetic semiconductor CrGeTe3 studied by THz spectroscopy".ACTA PHYSICA SINICA 71.23(2022).