  We study the 2D crystalline phases of paramagnetic colloidal particles with
dipolar interactions and constrained on a periodic substrate. Combining theory,
simulation, and experiments we demonstrate a new scenario of first-order phase
transitions that occurs via a complete inversion of the energy landscape,
featuring non-conventional properties that allow for: (i) tuning of crystal
symmetry; (ii) control of dynamical properties of different crystalline orders
via tuning of their relative stability with an external magnetic field; (iii)
an equivalent but independent control of the same dynamic properties via
temporal modulations of that field; and (iv) non-standard phase-ordering
kinetics involving spontaneous formation of transient metastable domains.
