Avalanches in the athermal 2d Random-Field Ising model: front propagation versus nucleation and growth dynamics

Abstract

The two-dimensional zero-temperature Random Field Ising Model with local adiabatic relaxation dynamics is studied. When externally driven, this model allows to analyse the properties of an advancing front for different amounts of disorder. By imposing special forced boundary conditions and allowing for systems with rectangular geometry, we favour the existence of a unique interface which is the boundary of a 1d spanning avalanche. We show that the description of an advancing front in terms of a univalued function x(y) lacks of a relevant contribution in the thermodynamic limit: the existence of overhangs and islands which are characteristic of the nucleation and growth dynamics