Two-orbital quantum spin model of magnetism in the iron pnictides

Article

关键词: HEISENBERG-ANTIFERROMAGNET;    LAYERED SUPERCONDUCTOR;    2 DIMENSIONS;    SYSTEMS;    ORDER;   

DOI  :  10.1103/PhysRevB.85.094410

来源: SCIE

【 摘 要 】

We study a two-orbital spin model to describe (pi, 0) stripe antiferromagnetism in the iron pnictides. The double-spin model has an on-site Hunds's coupling and intersite interactions extending to second neighbors (inter-and intraorbital) on the square lattice. Using a variational method based on a cluster decomposition, we optimize wave functions with up to eight cluster sites (up to 2(16) variational parameters). We focus on the anomalously small ordered moments in the stripe state of the pnictides. To account for it, and large variations among different compounds, we show that the second-neighbor cross-orbital exchange constant should be ferromagnetic, which leads to partially hidden stripe order, with a moment that can be varied over a large range by small changes in the coupling constants. In a different parameter region, we confirm the existence of a canted state previously found in spin-wave theory. We also identify several other phases of the model.

【 授权许可】

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