Broadening of a nonequilibrium phase transition by extended structural defects

TL;DR

This paper investigates how extended structural defects in a nonequilibrium system can smear the phase transition, leading to a gradual crossover instead of a sharp transition, using extremal statistics and simulations.

Contribution

It demonstrates that quenched extended impurities cause smearing of the nonequilibrium phase transition in directed percolation, a novel insight into disorder effects.

Findings

Extended impurities destroy the sharp phase transition.

Rare regions can undergo independent phase transitions.

Stationary states and dynamics are characterized by extremal statistics.

Abstract

We study the effects of quenched extended impurities on nonequilibrium phase transitions in the directed percolation universality class. We show that these impurities have a dramatic effect: they completely destroy the sharp phase transition by smearing. This is caused by rare strongly coupled spatial regions which can undergo the phase transition independently from the bulk system. We use extremal statistics to determine the stationary state as well as the dynamics in the tail of the smeared transition, and we illustrate the results by computer simulations.