1993/04/30 by Andrey V. Chubukov, Subir Sachdev, Jinwu Ye · 1 citation
Physics and Astronomy · #cond-mat
paper · pdf · doi:10.1103/physrevb.49.11919
published as Physical Review B 49, 11919 (1994) · 81 pages, REVTEX 3.0, smaller updated version, YCTP-xxxx
arxiv created 1994/02/04 · arxiv updated 2009/11/30
We present the general theory of clean, two-dimensional, quantum Heisenberg antiferromagnets which are close to the zero-temperature quantum transition between ground states with and without long-range Néel order. For Néel-ordered states, `nearly-critical' means that the ground state spin-stiffness, ρs, satisfies ρs ≪ J, where J is the nearest-neighbor exchange constant, while `nearly-critical' quantum-disordered ground states have a energy-gap, Δ, towards excitations with spin-1, which satisfies Δ≪ J. Under these circumstances, we show that the wavevector/frequency-dependent uniform and staggered spin susceptibilities, and the specific heat, are completely universal functions of just three thermodynamic parameters. Explicit results for the universal scaling functions are obtained by a 1/N expansion on the O(N) quantum non-linear sigma model, and by Monte Carlo simulations. These calculations lead to a variety of testable predictions for neutron scattering, NMR, and magnetization measurements. Our results are in good agreement with a number of numerical simulations and experiments on undoped and lightly-doped La2-δ SrδCu O4.