Time-resolved tracking of hot carrier relaxation in two types of MBenes

In metallic low-dimensional materials, the interaction between non-equilibrium electrons and phonons underlies various physical phenomena, such as the relaxation process of hot carriers. However, it is unclear how the surface, with or without termination, controls electron-phonon (e-p) interactions in two-dimensional (2D) transition metal borides (MBenes). Herein, ultrafast time-resolved spectroscopy was employed to measure the e-p interaction rate, revealing that MoB MBene without termination exhibits a lower rate than Mo_4/3B_2-x T _z MBene with termination, indicating that its e-p interactions are weakened. Raman spectra and computational calculations indicate that the suppression is attributed to the fact that the excited electrons can only couple with a limited number of vibrational modes. This study paves the way for the tailored manipulation of hot carrier relaxation time, offering opportunities for advanced applications in electronics, optoelectronics, catalysis, and more.