Interplay of topology and geometry in frustrated two-dimensional Heisenberg magnets

We investigate two-dimensional frustrated Heisenberg magnets using nonperturbative renormalization group techniques. These magnets allow for pointlike topological defects which are believed to unbind and drive either a crossover or a phase transition which separates a low-temperature, spin-wave-dominated regime from a high-temperature regime where defects are abundant. Our approach can account for the crossover qualitatively and both the temperature dependence of the correlation length as well as a broad but well-defined peak in the specific heat are reproduced. We find no signatures of a finite-temperature transition and an accompanying diverging length scale. Our analysis is consistent with a rapid crossover driven by topological defects.