Entropy scaling laws in self propelled glass formers

Abstract

Predicting transport from equilibrium structure is a challenging problem in liquid state physics. Here we probe a glass forming liquid composed of self-propelled “active” particles and show that increasing the duration of self-propulsion makes the pair excess entropy negatively larger. The associated reduction in the number of accessible configurations per particle leads to a reduction in self-diffusivity. At moderate supercooling, the self-diffusivity is Arrhenius and in a reduced form obeys a Dzugutov like scaling law, directly yielding us a pair excess entropy that is inversely proportional to the effective temperature. In the strongly super-cooled regime, Dzugutov law does not apply and we observe that, the pair excess entropy shows a non-Arrhenius (power law) dependence on the effective temperature with an exponent that depends on the self propulsion time of the active particles. To demonstrate the generality of our scaling laws in moderately high temperatures, we set the particle interactions to be purely repulsive in one case and Lennard-Jones in the other, and find that in both the cases, the reported high temperature scaling laws are robust over variations in the duration of self propulsion. Our results may apply to transport in active colloidal suspensions, passive tracers in bacterial baths, and self-propelled granular media, to mention a few.