Order metrics of amorphous solids: Structures, hyperuniformity, and implications for ultra-stable glasses

Abstract

Due to the lack of long-range order, it remains challenging to characterize the structure of disordered solids and understand the nature of the glass transition. Here we propose a new structural order parameter by taking into account multiple rotational symmetries. By studying its statistics for two-dimensional disordered packings of hard particles along the jamming transition line, we observe the evolution from disordered-particle-rich states to ordered-particle-rich states with the increase of packing fraction, together with the unusual non-monotonic change of the degree of hyperuniformity. At the high packing fraction end of the jamming transition line, the packings are mostly composed of ordered particles and are nearly hyperuniform beyond a finite length. Our work links the local order fluctuations to the thermodynamic stability and density fluctuations of disordered solids. Taking advantage of the order parameter, we propose the structural characteristic of ultra-stable glasses: Although globally disordered evaluated by any single symmetry, they are rich of ordered particles and effectively ‘globally ordered' with crystal-like density fluctuations.