Phase transition in the two-dimensional Heisenberg ferromagnet ${\mathrm{Fe}}_3{\mathrm{GeTe}}_2$ with long-range interaction

We demonstrate that phase transition and continuous symmetry breaking can happen in $2d$ Heisenberg ferromagnets with long range interaction in violation of the Hohenberg-Mermin-Wagner theorem. This has been possible to achieve in $2d$ van der Waals ferromagnet ${\text{Fe}}_3{\text{GeTe}}_2$ due to its exceptional tunability of magnetic properties. We argue that the variable critical exponent is a signature of phase transition in $2d$ systems with long range ordering, consistent with recent results from density functional theory and quantum Monte Carlo calculations.