Above-Curie-temperature ultrafast terahertz emission and spin current generation in a 2D superlattice...

The increasing demand for denser information storage and faster data processing has fueled a keen interest in exploring spin currents up to terahertz (THz) frequencies. Emergent 2D intrinsic magnetic materials constitute a novel and highly controllable platform to access such femtosecond spin dynamics at atomic layer thickness. However, the function of 2D van der Waals magnets are limited by their Curie temperatures, which are usually low. Here, in a 2D superlattice (Fe₃GeTe₂/CrSb)₃, we demonstrate ultrafast laser-induced spin current generation and THz radiation at room temperature, overcoming the challenge of the Curie temperature of Fe₃GeTe₂ being only 206 K. In tandem with time-resolved magneto-optical Kerr effect measurements and first-principles calculations, we further elucidate the origin of the spin currents-a laser-enhanced proximity effect manifested as a laser-induced reduction of interlayer distance and enhanced electron exchange interactions, which causes transient spin polarization in the heterostructure. Our findings present an innovative, magnetic-element-free route for generating ultrafast spin currents within the 2D limit, underscoring the significant potential of laser THz emission spectroscopy in investigating laser-induced extraordinary spin dynamics.