2004/08/31 by Andreas Lüscher, Andreas Luscher, O. P. Sushkov +1 · 2 citations
Physics and Astronomy · #Advanced Condensed Matter Physics #Antiferromagnetism #Condensed matter physics #Dynamics (music) #Heisenberg model #Impurity #Materials science #Physics #Physics of Superconductivity and Magnetism #Quantum mechanics #Range (aeronautics) #Theoretical and Computational Physics #cond-mat.str-el
paper · pdf · doi:10.1103/physrevb.71.064414
published as Phys. Rev. B 71, 064414 (2005) · 6 pages, 5 figures
arxiv created 2004/11/15 · openalex publication_date 2005/02/23 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
We consider a two-dimensional Heisenberg antiferromagnet on a square lattice with weakly coupled impurities, i.e., additional spins interacting with the host magnet by a small dimensionless coupling constant g⪡1. Using linear spin-wave theory, we find that the magnetization disturbance at distance r from a single impurity behaves as \ensuremathδSz\ensuremath∝g∕r for 1⪡r⪡1∕g and as \ensuremathδSz\ensuremath∝1∕(gr3) for r⪢1∕g. Surprisingly the magnetization disturbance is inversely proportional to the coupling constant. The interaction between two impurities separated by a distance r is \ensuremathδϵ\ensuremath∝g2∕r for 1⪡r⪡1∕g and \ensuremathδϵ\ensuremath∝1∕r3 for r⪢1∕g. For large distances, the interaction is therefore universal and independent of the coupling constant. We have also found that the frequency of Rabi oscillations between two impurities is logarithmically enhanced compared to the decay width \ensuremathωRabi\ensuremath∝g2\phantom\rule0.2em0exln(1∕gr) at 1⪡r⪡1∕g. This leads to a logarithmic enhancement for NMR and EPR line broadening. All these astonishing results are due to the gapless spectrum of magnetic excitations in the quantum antiferromagnet.