What stabilizes skyrmion lattices in centrosymmetric magnets like Gd2PdSi3?
In plain words
Most skyrmions appear in crystals lacking mirror symmetry, where a twisting interaction favors them. Gd2PdSi3 and GdRu2Si2 have that symmetry yet host very small skyrmions, and the competing explanations involve geometric frustration or interactions carried by conduction electrons.
Precise statement
For Gd2PdSi3 (triangular) and GdRu2Si2 (tetragonal), with skyrmion-lattice periods of about 2 to 3 nm, determine which mechanism stabilizes the multi-$q$ state: frustrated RKKY couplings, Fermi-surface-driven biquadratic and four-spin interactions, or dipolar and anisotropy effects. An answer is a microscopic model derived from the measured band structure that reproduces the field-temperature phase diagram and the modulation vectors.
What would settle it
Ab initio spin models compared with resonant x-ray and neutron data over the full phase diagram, plus pressure or doping tuning of the Fermi surface.