2003/03/04 by Subir Sachdev, Matthias Vojta
Physics and Astronomy · #cond-mat.str-el #cond-mat.supr-con #hep-th
paper · pdf · doi:10.1103/physrevb.68.064419
published as Phys.Rev. B68 (2003) 064419 · 14 pages, 7 figures; (v2) added ref
arxiv created 2003/03/04 · arxiv updated 2009/11/30
We present a new formulation of the theory of an arbitrary quantum impurity in an antiferromagnet, using the O(3) non-linear sigma model. We obtain the low temperature expansion for the impurity spin susceptibilities of antiferromagnets with magnetic long-range order in the ground state. We also consider the bulk quantum phase transition in d=2 to the gapped paramagnet (d is the spatial dimension): the impurity is described solely by a topological Berry phase term which is an exactly marginal perturbation to the critical theory. The physical properties of the quantum impurity near criticality are obtained by an expansion in (d-1).