Phonon-related monochromatic THz radiation and its magneto-modulation in 2D ferromagnetic Cr2Ge2Te6

TL;DR

This paper demonstrates a magneto-tunable, monochromatic THz radiation source using 2D ferromagnetic Cr2Ge2Te6, with potential applications in photonics and spintronics, driven by phonon-polariton emission influenced by magnetic fields and temperature.

Contribution

First demonstration of a magneto-modulated monochromatic THz source based on 2D ferromagnetic Cr2Ge2Te6 with high efficiency and tunability.

Findings

Generated ~0.9 THz radiation with 2.1% efficiency at 160 K.

THz emission modulated by magnetic field below 160 K.

Emission identified as phonon-polariton related, showing strong spin-lattice coupling.

Abstract

Searching multiple types of terahertz (THz) irradiation source is crucial for the THz technology. Here, by utilizing a two-dimensional (2D) ferromagnetic Cr2Ge2Te6 crystal, we firstly demonstrate a magneto-tunable monochromatic THz irradiation source. 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 the 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 confirmed 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.