2004/02/29 by Kaj H. Hoglund, Kaj H. Höglund, Anders W. Sandvik · 2 citations
Physics and Astronomy · #Advanced Condensed Matter Physics #Physics of Superconductivity and Magnetism #Theoretical and Computational Physics #cond-mat.str-el
paper · pdf · doi:10.1103/physrevb.70.024406
published as Phys. Rev. B 70, 024406 (2004) · 15 pages, 14 figures, submitted to PRB. v2, published version with cosmetic changes
openalex publication_date 2004/07/12 · arxiv created 2004/07/16 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/28
We discuss effects of various impurities on the magnetic susceptibility and the specific heat of the quantum S=1∕2 Heisenberg antiferromagnet on a two-dimensional square lattice. For impurities with spin Si>0 (here Si=1∕2 in the case of a vacancy or an added spin, and Si=1 for a spin coupled ferromagnetically to its neighbors), our quantum Monte Carlo simulations confirm a classical-like Curie susceptibility contribution Si2∕3T, which originates from an alignment of the impurity spin with the local N'eel order. In addition, we find a logarithmically divergent contribution, which we attribute to fluctuations transverse to the local N'eel vector. We also study frustrated and nonfrustrated bond impurities with Si=0. For a simple intuitive picture of the impurity problem, we discuss an effective few-spin model that can distinguish between the different impurities and reproduces the leading-order simulation data over a wide temperature range.