Abstract
Searching multiple types of terahertz (THz) irradiation source is crucial for the THz technology. In addition to the conventional fermionic cases, bosonic quasi‐/particles also promise energy‐efficient THz wave emission. Here, by utilizing a 2D ferromagnetic Cr2Ge2Te6 crystal, first a phonon‐related magneto‐tunable monochromatic THz irradiation source is demonstrated. With a low‐photonic‐energy broadband THz pump, a strong THz irradiation with frequency ≈0.9 THz and bandwidth ≈0.25 THz can be generated and its conversion efficiency could even reach 2.1% at 160 K. Moreover, it is intriguing to find that such monochromatic THz irradiation can be efficiently modulated by external magnetic field below 160 K. According to both experimental and theoretical analyses, the emergent THz irradiation is identified as the emission from the phonon‐polariton and its temperature and magnetic field dependent behaviors confirm the large spin‐lattice coupling in this 2D ferromagnetic crystal. These observations provide a new route for the creation of tunable monochromatic THz source which may have great practical interests in future applications in photonic and spintronic devices.
Highlights
Terahertz (THz) radiation source plays a crucial role in relevant research and applications
In addition to the general fermionic cases, our findings suggest that the use of 2D van der Waals (vdWs) ferromagnet might provide a viable source for the realization of bosonic THz source with tunable and monochromatic features, which may have great practical interests in future applications in photonic and spintronic devices
Summary
Terahertz (THz) radiation source plays a crucial role in relevant research and applications. With extraordinary electrical and optical properties, 2D van der Waals (vdWs) materials has been used for the novel THz irradiation source developing.[7] For instance, Xu et al reported the THz surface emission based on the competition between surface optical rectification and photocurrent surge in layered MoS2.8 Under the excitation of strong infrared pulses, Ma et al proposed a new THz emitter based on the shift current occurring on the inversion-broken surface of layered CrSiTe3 crystal.[9] With the aid of laser excited surface plasmon on gold substrate, Bahk et al observed an enhanced THz emission from the single-layered graphene.[10] In the majority of these studies, THz radiation based on 2D vdWs materials are originating from photoconductive effect, optical rectification, laser induced plasma, which all belong to the fermion (electron) catalog and generally bring broadband THz emission with low conversion efficiency
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