Ordered droplets in quantum magnets with long-range interactions
A defect coupling to the square of the order parameter in a nearly quantum-critical magnet can nucleate an ordered droplet while the bulk system is in the paramagnetic phase. We study the influence of long-range spatial interactions of the form $r^{-(d+σ)}$ on the droplet formation. To this end, we solve a Landau-Ginzburg-Wilson free energy in saddle point approximation. The long-range interaction causes the droplet to develop an energetically unfavorable power-law tail. However, for $σ>0$, the free energy contribution of this tail is subleading in the limit of large droplets; and the droplet formation is controlled by the defect bulk. Thus, for large defects, long-range interactions do not hinder the formation of droplets.
cond-mat.str-el↗