Theory of partial quantum disorder in the stuffed honeycomb Heisenberg antiferromagnet

Urban F. P. Seifert and Matthias Vojta
Phys. Rev. B 99, 155156 – Published 30 April 2019

Abstract

Recent numerical results [Gonzalez et al., Phys. Rev. Lett. 122, 017201 (2019); Shimada et al., J. Phys. Conf. Ser. 969, 012126 (2018)] point to the existence of a partial-disorder ground state for a spin-1/2 antiferromagnet on the stuffed honeycomb lattice, with 2/3 of the local moments ordering in an antiferromagnetic Néel pattern, while the remaining 1/3 of the sites display short-range correlations only, akin to a quantum spin liquid. We derive an effective model for this disordered subsystem, by integrating out fluctuations of the ordered local moments, which yield couplings in a formal 1/S expansion, with S being the spin amplitude. The result is an effective triangular-lattice XXZ model, with planar ferromagnetic order for large S and a stripe-ordered Ising ground state for small S, the latter being the result of frustrated Ising interactions. Within the semiclassical analysis, the transition point between the two orders is located at Sc=0.646, being very close to the relevant case S=1/2. Near S=Sc quantum fluctuations tend to destabilize magnetic order. We conjecture that this applies to S=1/2, thus explaining the observed partial-disorder state.

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  • Received 30 December 2018

DOI:https://doi.org/10.1103/PhysRevB.99.155156

©2019 American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Urban F. P. Seifert and Matthias Vojta

  • Institut für Theoretische Physik and Würzburg-Dresden Cluster of Excellence ct.qmat, Technische Universität Dresden, 01062 Dresden, Germany

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Issue

Vol. 99, Iss. 15 — 15 April 2019

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