Co2MnGa is ferromagnetic Heusler compound which can change their size by up to 10% in a magnetic field. This indicates their electrons are subject of internal stress and when magnetic field tries to reorient, they expand whole crystal lattice. By general understanding the electrons only mediate attractive forces between atoms. But similarly to human society where racism and bullying often takes place, the position of electrons between atoms isn't such a simple. Sometimes attractive forces are mediated by elongated orbitals protruding from surface of atoms and their attractions sqeezes and expels movable electrons from inner layers. Such an electrons behave like mercury in pores of brick, from where it gets expelled to surface, where it's forming conductive surface layer.
Physicists are calling these materials topological insulators, because they lose conductivity in the center on behalf of increased conductivity at their surface. With compare to metals, which are also soaked by electrons, the surface electrons are subject of internal stress because they repel each other like water on surface of hydrophobic material or like minorities people on perimeter of xenophobic society. Such an electrons propagate along surface not in transverse waves like ripples at the water surface, but merely like vortices, which behave like less or more independent particles.
With compare to common topological insulators the Heusler ferromagnetic insulators don't sqeeze electrons betwwen atoms by Coulombic forces but they behave like tiny magnets which are arranged in repulsive arrangement, so that their electrons get also stressed, but in perpendicular way, than the electrons in normal topological insulators. Their vortices aren't arranged and locked perpendicularly to surface like sunspots
, but in parallel and they move around here like Falaco solitons in mutually locked pairs, so called Weyl fermions, which resemble the Cooper pairs at the surface of superconductors - they're not composed of electron pairs though, but from their magnetic vortices.
The above observation is thus quite significant and analogous to observation of room temperature superconductivity. The common behavior of strong ferromagnets and superconductors is, they're often very brittle, which indicates strong internal stress within material. This stress also manifests itself by buckling of surface electrons, which undulate like membrane of drum perpendicularly to surface (surface polarons), whereas electrons at the surface of ordinary metals merely form ripples parallel with surface (surface plasmons). They're thus forming pressure waves in analogy to scalar waves of Nicola Tesla rather than transverse waves of light.
Weeyl fermion materials are supposed to find application in spinotronic and magnetic recording media - but for me they're interesting primarily because of their potential utilization in overunity applications. Their surface buckling could behave in similar way, like surface buckling of graphene, which was already found to be able to generate electricity from ambient heat.
