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.
T. Vojta and J. A. Hoyos, "Ordered Droplets in Quantum Magnets with Long-Range Interactions," Physica B: Condensed Matter, Elsevier, Apr 2008.
The definitive version is available at http://dx.doi.org/10.1016/j.physb.2007.10.252
National Science Foundation (U.S.)
Keywords and Phrases
Defect Disorder; Griffiths Singularity; Quantum Phase Transition
Article - Journal
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