Hyperuniformity: unconventional ordering out of equilibrium

The properties of materials are often understood in terms of their structure and symmetries. 

Order is often manifested in correlations of an order parameter that extends throughout the system. In this talk I will discuss an exotic ordering that is paradoxically found in disordered systems. This ordering is known as hyperuniformity, and is defined as having suppressed fluctuations on arbitrary long length scales. While the fluctuations of a random uncorrelated arrangement of particles scales as the enclosed volume, hyperuniform fluctuations grow as the volume^alpha, with alpha<1. 

I will discuss the occurrence of hyperuniformity in two distinct non-equilibrium phase transitions: (1) An absorbing phase transition found in sheared colloidal suspensions. (2) The jamming transitions of soft spheres at zero temperature. Hyperuniformity in these systems is manifested in two different fields and is characterized by different exponents. Interestingly, near both these transitions there are two different diverging correlation lengths. Our work demonstrates that exotic order can be hidden in plain sight, and that structures that form out of equilibrium may be fundamentally different from their equilibrium counterparts.