arXiv subjects

Stefano Iubini

Publications and source records attributed to Stefano Iubini.

39 records · Page 3Linked to original sources

arXiv2015

Energy and magnetisation transport in non-equilibrium macrospin systems

We investigate numerically the magnetisation dynamics of an array of nano-disks interacting through the magneto-dipolar coupling. In the presence of a temperature gradient, the chain reaches a non-equilibrium steady state where energy and magnetisation currents propagate. This effect can be described as the flow of energy and particle currents in an off-equilibrium discrete nonlinear Schrödinger (DNLS) equation. This model makes transparent the transport properties of the system and allows for a precise definition of temperature and chemical potential for a precessing spin. The present study proposes a novel setup for the spin-Seebeck effect, and shows that its qualitative features can be captured by a general oscillator-chain model

cond-mat.stat-mech↗

arXiv2014

Boundary-induced instabilities in coupled oscillators

A novel class of nonequilibrium phase-transitions at zero temperature is found in chains of nonlinear oscillators.For two paradigmatic systems, the Hamiltonian XY model and the discrete nonlinear Schrödinger equation, we find that the application of boundary forces induces two synchronized phases, separated by a non-trivial interfacial region where the kinetic temperature is finite. Dynamics in such supercritical state displays anomalous chaotic properties whereby some observables are non-extensive and transport is superdiffusive. At finite temperatures, the transition is smoothed, but the temperature profile is still non-monotonous.

nlin.CD↗

arXiv2013

Coarsening dynamics in a simplified DNLS model

We investigate the coarsening evolution occurring in a simplified stochastic model of the Discrete NonLinear Schrödinger (DNLS) equation in the so-called negative-temperature region. We provide an explanation of the coarsening exponent $n=1/3$, by invoking an analogy with a suitable exclusion process. In spite of the equivalence with the exponent observed in other known universality classes, this model is certainly different, in that it refers to a dynamics with two conservation laws.

cond-mat.stat-mech↗