Hidden and universal relaxation mode in metallic glasses of simple atomic structure

Relaxation inherently relates to the nonequilibrium nature of glassy solids and has profound influences on their properties. Exploring diverse relaxation modes of glasses is central to understanding their complicated dynamic behaviors and the nature of glass transition. Here, we report a hidden and universal relaxation mode (termed ${\ensuremath{\alpha}}^{\ensuremath{'}}$ relaxation)---which emerges between \ensuremath{\alpha} relaxation and \ensuremath{\beta} relaxation in metallic glasses with relatively simple atomic structure---by systematically investigating their dynamic modulus spectrum. We find that the excitation of the ${\ensuremath{\alpha}}^{\ensuremath{'}}$ relaxation mode is controlled by the energy state and the local potential energy topology around the state. A notable ${\ensuremath{\alpha}}^{\ensuremath{'}}$ relaxation can only appear at an intermediate range of energy states, and it can be manipulated by annealing or rejuvenating. The activation energy and the nonmonotonic behavior of ${\ensuremath{\alpha}}^{\ensuremath{'}}$ relaxation reveal that it intrinsically connects \ensuremath{\alpha} relaxation and \ensuremath{\beta} relaxation. Furthermore, we also show that the excitation of the ${\ensuremath{\alpha}}^{\ensuremath{'}}$ relaxation mode, rather than the level of the energy state, can notably improve the homogeneous tensile deformability of metallic glasses.