Thermal Effects in the dynamics of disordered elastic systems

TL;DR

This paper investigates how temperature influences the depinning transition in disordered elastic systems, revealing that thermal effects round the transition and challenging the analogy with standard critical phenomena.

Contribution

It introduces a novel algorithm to study depinning near the threshold and demonstrates that the critical phenomena analogy does not fully apply at finite temperatures.

Findings

Temperature causes a rounding of the depinning transition.

No divergent lengthscale exists below the depinning threshold at finite temperature.

A new exponent characterizes the thermal rounding of depinning.

Abstract

Many seemingly different macroscopic systems (magnets, ferroelectrics, CDW, vortices,..) can be described as generic disordered elastic systems. Understanding their static and dynamics thus poses challenging problems both from the point of view of fundamental physics and of practical applications. Despite important progress many questions remain open. In particular the temperature has drastic effects on the way these systems respond to an external force. We address here the important question of the thermal effect close to depinning, and whether these effects can be understood in the analogy with standard critical phenomena, analogy so useful to understand the zero temperature case. We show that close to the depinning force temperature leads to a rounding of the depinning transition and compute the corresponding exponent. In addition, using a novel algorithm it is possible to study precisely the behavior close to depinning, and to show that the commonly accepted analogy of the depinning with a critical phenomenon does not fully hold, since no divergent lengthscale exists in the steady state properties of the line below the depinning threshold.