Ultrafast dynamics in Tb₂Te₅ single crystals

Recently, the Tb₂Te₅ single crystals have been successfully grown by evaporating liquid tellurium from a tellurium-terbium liquid in a boomerang-shaped quartz glass ampoule. The crystal structure of Tb₂Te₅ is orthorhombic Cmcm space group with a = 4.3009(17)Å, b = 43.107(18)Å, c = 4.3016(17)Å, which was characterized by the single crystal X-ray diffraction experiment at 100 K. Additionally, there are two antiferromagnetic orders at T_N1 = 9.0 K and T_N2 = 6.8 K, respectively. In this report, we study the ultrafast dynamics of Tb₂Te₅ single crystals at various temperatures by using pump-probe spectroscopy. The transient reflectivity change spectra (ΔR/R) exhibit a rapid rise due to the generation of photoexcited carriers, concurrent with ultrafast demagnetization. The subsequent relaxation involves multiple processes, including a fast decay (~ps) attributed to carrier relaxation primarily through electron-phonon coupling, and a slower relaxation process (~100 ps) associated with the recovery of magnetic order. The temperature-dependent results further reveal the interaction between the magnetic and electronic subsystems in Tb₂Te₅.