  Relaxation dynamics, as a key to understand glass formation and glassy
properties, remains an elusive and challenging issue in condensed matter
physics. In this work, in situ high-pressure synchrotron high-energy x-ray
photon correlation spectroscopy has been developed to probe the atomic-scale
relaxation dynamics of a cerium-based metallic glass during compression.
Although the sample density continuously increases, the collective atomic
motion initially slows down as generally expected and then counter-intuitively
accelerates with further compression (density increase), showing an unusual
non-monotonic pressure-induced steady relaxation dynamics crossover at ~3 GPa.
Furthermore, by combining in situ high-pressure synchrotron x-ray diffraction,
the relaxation dynamics anomaly is evidenced to closely correlate with the
dramatic changes in local atomic structures during compression, rather than
monotonically scaling with either sample density or overall stress level. These
findings could provide new insight into relaxation dynamics and their
relationship with local atomic structures of glasses.
