How does a two-dimensional skyrmion lattice melt?
In plain words
A sheet of skyrmions can melt like a 2D crystal, possibly through an intermediate hexatic phase that keeps orientation order but loses positional order. Whether this two-step melting is generic, and how pinning changes it, is open.
Precise statement
For a 2D skyrmion lattice in a thin chiral magnet, determine whether melting follows the two-step KTHNY scenario (solid to hexatic to liquid via Kosterlitz-Thouless transitions, with $\eta_6=1/4$ at the hexatic-liquid transition) or a first-order transition, and how quenched pinning changes the sequence. An answer is the measured or simulated phase diagram with correlation-function exponents.
What would settle it
Real-space imaging of skyrmion positions in clean films across temperature, analyzed for translational and orientational correlations, with simulations using the measured pinning.
Status in the literature
Huang et al. (Nature Nanotechnology 2020) observed a hexatic skyrmion phase in thin Cu2OSeO3.