Liquid-liquid transition revealed by quasi-static cooling of an ultra-viscous metallic liquid

Abstract: Temperature-driven polyamorphism has been reported in various supercooled liquids and glasses. The dynamical and structural routes followed by the system during such crossovers are however not universal and appear to be related to intrinsic kinetic properties of the liquid. By combining x-ray photon correlation spectroscopy and high energy x-ray diffraction, we have followed the collective atomic motion and structural changes during quasi-static cooling of the Au49Cu26.9Si16.3Ag5.5Pd2.3 metallic glass-former. Due to this ultra-slow thermal protocol, the glass transition temperature is lowered far enough to reveal a liquid-liquid crossover in the ultra-viscous supercooled phase. This transition is usually hidden by vitrification and leads to a strong liquid characterized by increasing correlation at the medium range.