Density of scattering resonances in a disordered system
Mikhail Kurilov
Nanocenter CENN, Slovenia
Reflection of particles from a disordered or chaotic medium is characterized by a scattering matrix that can be represented as a superposition of resonances. Each resonance corresponds to an eigenstate inside the medium and has a width related to the decay time of this eigenstate. We develop a general approach to study the distribution function of these resonance widths based on the nonlinear sigma model. We derive an integral representation of the distribution function that works equally well for systems of any symmetry and for any type of coupling to the measuring device. From this integral representation we find explicit analytic expressions for the distribution function in the case of disordered metallic grains. We also compare the analytic results to large-scale numerical simulations and observe their perfect agreement.
Related publication:
arXiv:2512.18717
Effect of superconductivity on non-uniform magnetization in disordered Superconductor-Ferromagnet junctions
Andrei Levin
Nanocenter CENN, Slovenia
We study proximity effect in a tunnel junction between a bulk superconductor and a thin disordered ferromagnetic layer on its surface. Cooper pairs penetrating from the superconductor into the ferromagnet tend to destabilize its uniform magnetic order. Competition of this effect and intrinsic magnetic stiffness of the ferromagnet leads to a second-order phase transition between uniform and non-uniform magnetic states. Using semiclassical Usadel equations, we derive Landau functional for this transition and construct complete phase diagram of the system.
Related publication:
arXiv:2512.08044