Sommaire:

The response of spatially extended systems to a force leading their dynamics out of equilibrium is strongly affected by the presence of disorder. An archetypal class of systems where this scenario is found is given by extended elastic objects (lines or manifolds) which fluctuate in an heterogeneous medium. Examples range from interfaces in magnetic or ferroic materials, contact lines, charge density waves and vortices in superconductors, to solid membranes in chemical or biological liquids, and fronts in liquid crystals. In this talk I will discuss about two recent research works focusing on this type of system. In a first part I will focus on the so-called creep motion at finite temperature, a regime with highly non-linear, stretched-exponential velocity–force relation. I will introduce an effective model describing the motion of the driven interface at fixed length scale, allowing to recover the creep law, to extend the description of the dynamics from low forces to larger forces, and to characterize the crossover between creep and linear response in finite systems in the very small force regime. In the second part of the talk I will focus on zero-temperature avalanche dynamics at the depinning transition. I will discuss about the amount of energy released in individual avalanches, a question that is relevant not only for these kind of systems, but also for amorphous materials. The scaling of the energy of an avalanche with its size is controlled by a new exponent, recently found in the so far unrelated context of the thermal rounding of the depinning transition. Based on the results of this study I will propose a new numerical method to determine the dynamic exponent at the depinning transition relying on automata-like quasi-static simulations, which are way less costly than simulating real time dynamics.

Pour plus d'informations, merci de contacter Coslovich D.