Low-energy properties of anisotropic two-dimensional spin-1/2 Heisenberg models in staggered magnetic fields
Low-energy properties of anisotropic two-dimensional spin-1/2 Heisenberg models in staggered magnetic fields
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交错磁场中各向异性二维自旋 1/2 海森堡模型的低能特性
DOI：
10.1103/physrevb.84.134407
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发表时间：
2011-06
影响因子：
3.7
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中科院分区：
文献类型：
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我们对二维交错磁场中的各向异性自旋 1/2 海森堡模型进行了系统研究。为了模拟真实材料，我们考虑了一个耦合的反铁磁链系统，其链间相互作用可以是铁磁的，也可以是反铁磁的。当交错场与磁相互作用相当时，能隙立即打开，并遵循幂律作为施加场的函数，类似于一维的情况。当场与相互作用竞争时，会发生量子相变（QPT），从低场下的无间隙、磁有序相到有间隙、无序状态。我们使用连续时间蒙特卡罗方法来计算有序相的交错矩和无序相的自旋间隙。我们将相图推导为各向异性比和应用场的函数，并计算模型在两个量上的缩放行为。我们证明，在竞争情况下，交错场的作用是维持 QPT 周围的准一维行为，并因此讨论从一维 (1D) 物理到二维物理交叉的本质。
We present a systematic study of the anisotropic spin-1/2 Heisenberg model in staggered magnetic fields in two dimensions. To mimic real materials, we consider a system of coupled, antiferromagnetic chains, whose interchain interaction can be either ferro-or antiferromagnetic. When the staggered field is commensurate with the magnetic interactions, an energy gap opens immediately and follows a power law as a function of the applied field, similar to the situation in one dimension. When the field competes with the interactions, a quantum phase transition (QPT) occurs from a gapless, magnetically ordered phase at low fields to a gapped, disordered regime. We use a continuous-time Monte Carlo method to compute the staggered moment of the ordered phases and the spin gap of the disordered phases. We deduce the phase diagrams as functions of the anisotropy ratio and the applied field, and calculate the scaling behavior of the models in both quantities. We show that in the competitive case, the staggered field acts to maintain a regime of quasi-1D behavior around the QPT, and we discuss as a consequence the nature of the crossover from one-dimensional (1D) to 2D physics.