Complex Systems and Materials (CSM)

Leader: Prof. Mikko Alava

The CSM group applies statistical physics to a wide variety of cross-disciplinary topics, ranging from computer science to materials as paper to complex networks. We also interact with industrial research, and study fundamental issues both theoretically and experimentally. The research pages show some recent highlights about these.

Strain-rate map in paper

This colorful picture shows the local strain rates during a creep fracture experiment (courtesy of Juha Koivisto). Clearly to describe these fluctuations one needs not only colours but also a toolbox, and we apply statistical physics to this end (See the research page for more examples).

Damage profiles in fracture

Statistical fracture mechanics is one field where one can study fundamental theoretical phenomena (non-equilibrium phase transiti1ons, self-organized criticality, finite size scaling …) and apply them to engineering -related problems. This figure (Physical Review Letters 100, 055502) depicts the damage cloud around a defect in fracture.

Academy Research Fellow Lasse Laurson carries out independent research activities related to dynamical processes in various material science applications. One of the main focus areas of research of Laurson is theory and modeling of domain wall dynamics in low-dimensional ferromagnets (thin films and nanowires). This is the area of the Helsinki Institute of Physics Theory Programme project on Domain Wall Dynamics, which Laurson leads. The research is done in collaboration both locally within Aalto University (e.g. with the NanoSpin group of Prof. Sebastiaan van Dijken) and across Europe, in particular via an associated partnership in the European Commission ITN project “WALL”, with Laurson the Scientist in Charge of the project at Aalto. Laurson is also actively involved in many research topics of the CSM group, including fracture, plasticity and friction. The latter project is also related to a COST network “Understanding and Controlling Nano and Mesoscale Friction”.

Spatial structure of Barkhausen jumps or avalanches in a model of a domain wall in thin films with uniaxial in-plane anisotropy. When tuning an experimentally controllable parameter, we observe a crossover between two universality classes of the avalanche dynamics, with a related change from “zigzag” (top) to rough (bottom) domain wall morphology (see the arxiv preprint for our recent paper).

Zigzag domain walls