Spin Correlation Functions in the Large-α Region of the Square-Lattice J_1-J_2 Model (General)

概要

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In the context of modified spin-wave theory, we perform a finite-temperature spin-wave calculation in the large-α region of the J_1-J_2 model, where α = J_2/J_1. The spin correlation functions for large separations are calculated and the correlation lengths at very low temperatures are given. The two-types of spin correlation functions with a spatial anisotropy are obtained, and each of them is expressed in terms of the two different correlation lengths. At α → ∞, the J_1-J_2 model on the square lattice with a lattice spacing a should physically be divided into the two disconnected square-lattice antiferromagnets with a lattice spacing √<2>a. At this limit, one of our two correlation functions vanishes and the other is correctly reduced to the one in the square-lattice antiferromagnet. Also the two correlation lengths are unified and are reduced to the one in the above square-lattice antiferromagnet.
社団法人日本物理学会の論文
2004-03-15