Quantum Phase Transition in the Frustrated Heisenberg Antiferromagnet
arXiv:cond-mat/9406106 · doi:10.1103/PhysRevB.50.13821
Abstract
Using the J_1-J_2 model, we present a description of quantum phase transition from Neel ordered to the spin-liquid state based on the modified spin wave theory. The general expression for the gap in the spectrum in the spin-liquid phase is presented.
8 pages of REVTeX 3.0, one PostScript file appended (Eq. 15 corrected, two recent references added, + some minor changes)