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Glasses are known for their intrinsic structural disorder. Here, Wu et al. uncover the hidden spatial organization of topological defects embedded in vibrational eigenmodes, and reveal how these defects govern the emergence of plastic flow under shear.

The medium range order in amorphous materials has a profound impact on their properties. Yuan et al. investigate how non-spherical particle shape affects granular packing and reveal amorphous-amorphous transitions associated with an orientational order of particles at intermediate length scales.

Viable methods for the production of ultrastable glasses are much sought after. A potential approach for creating bulk ultrastable glasses, based on random particle bonding scenarios, is now numerically investigated. The method is expected to be applicable to molecular and colloidal glasses.

Glasses show peculiar relaxation dynamics below glass transition temperature, yet a deeper understanding of this phenomenon is still lacking. Wu et al. show the coexistence of stretched and compressed relaxation in a metallic glass system and attribute their origins to different local cluster structures.

Glass-forming liquids are generally thought to relax through a collective rearrangement of domains, correlated over a length scale that increases with decreasing temperature. A numerical study now reveals a surprising twist to the story, claiming that relaxation depends non-monotonically on temperature.

Granular materials exhibit yielding behaviors rather different from glasses that can be elastic. Here, Yuan et al. show a cross-over from creep to diffusive dynamics in three-dimensional granular systems under cyclic shear and that the relaxation process depends on the roughness of the constituent particles.

It remains challenging to understand the relation between mechanical properties of glasses close to the yielding point and plastic behaviors at microscales. Wu et al. examine the plasticity using topological properties of the vibrational modes and identify a correlation between defects and plastic events.

The onset of rigidity in a two-dimensional colloidal glass-forming system is identified by the formation and merging of locally rigid domains in which particles move in a cooperative manner.

It is a general consensus that the structural defects are the plasticity carriers in amorphous solids, but its microscopic view remains largely unknown. Cao et a. show that highly distorted coplanar tetrahedra act as defects in granular packings, which flip under shear to carry local plasticity.

The relaxation dynamics of granular materials is more like that of complex fluids than that of thermal glass-forming systems, owing to the absence of the ‘cage effect’.