Pathology of Schwinger boson mean-field theory for Heisenberg spin models

Theja N. De Silva, Michael Ma, Fu Chun Zhang

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Abstract

We reanalyze the Schwinger boson mean-field theory (SBMFT) for Heisenberg spin models on the cubic lattice. We find that the second-order phase-transition point for magnetic ordering previously reported corresponds to a local maximum of the free-energy functional. For both ferromagnetic and antiferromagnetic Heisenberg models with spin S ≥ SC, where SC < 1/2, the mean-field transitions are first-order from the magnetically long-ranged ordered phase to the completely uncorrelated phase. In addition to erroneously giving a first-order transition for magnetic ordering, the mean-field theory does not include a phase with finite short-range correlation, thus negating one of the prime advantages of SBMFT. The relevance of these pathologies to other situations beyond the cubic lattice is discussed.

Original languageEnglish (US)
Article number104417
Pages (from-to)1044171-1044176
Number of pages6
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume66
Issue number10
DOIs
Publication statusPublished - Sep 17 2002

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ASJC Scopus subject areas

  • Condensed Matter Physics

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