Dynamic Phases of Active Matter Systems with Quenched Disorder

TL;DR

This paper explores how active matter systems with quenched disorder exhibit complex depinning and sliding transitions, revealing new nonequilibrium phases and morphologies driven by external forces.

Contribution

It introduces a new class of active matter systems with quenched disorder that show rich depinning phenomena and phase transitions, expanding understanding of nonequilibrium dynamics.

Findings

Identification of multiple dynamical phases including pinned, flowing, and phase-separated states.

Mapping of phase diagrams as functions of drive, substrate strength, and propulsion length.

Observation of novel nonequilibrium transitions unique to active matter with disorder.

Abstract

Depinning and nonequilibrium transitions within sliding states in systems driven over quenched disorder arise across a wide spectrum of size scales ranging from atomic friction at the nanoscale, flux motion in type-II superconductors at the mesoscale, colloidal motion in disordered media at the microscale, and plate tectonics at geological length scales. Here we show that active matter or self-propelled particles interacting with quenched disorder under an external drive represents a new class of system that can also exhibit pinning-depinning phenomena, plastic flow phases, and nonequilibrium sliding transitions that are correlated with distinct morphologies and velocity-force curve signatures. When interactions with the substrate are strong, a homogeneous pinned liquid phase forms that depins plastically into a uniform disordered phase and then dynamically transitions first into a moving stripe coexisting with a pinned liquid and then into a moving phase separated state at higher drives. We numerically map the resulting dynamical phase diagrams as a function of external drive, substrate interaction strength, and self-propulsion correlation length. These phases can be observed for active matter moving through random disorder. Our results indicate that intrinsically nonequilibrium systems can exhibit additional nonequilibrium transitions when subjected to an external drive.