Quantum fluctuations and excitations in antiferromagnetic quasicrystals
Quantum fluctuations and excitations in antiferromagnetic quasicrystals
复制标题
反铁磁准晶体中的量子涨落和激发
DOI：
10.1103/physrevb.71.104427
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发表时间：
2004
影响因子：
3.7
通讯作者：
I. Milat
中科院分区：
文献类型：
--
作者：
S. Wessel;I. Milat
通过数值求解有限近似的八角形瓦片上的线性自旋波理论，研究了反铁磁海森堡模型的量子涨落和激发谱对二维准晶的影响。在这一近似方案下，量子蒙特卡罗计算的局域交错磁矩分布和静态自旋结构因子得到了很好的重现。此外，磁激发谱由类磁振子的低能模以及具有多重分形性质的无色散高能态组成。动力学自旋结构因子可用于非弹性中子散射，在低能呈现线性软模，在中能出现分叉的自相似结构，在高能区呈现平带。我们发现，由准周期结构的不均匀引起的局域交错力矩的分布导致了局域动力学自旋磁化率的特征能量扩散，这意味着不同的局域环境下具有不同的核磁共振谱。
We study the effects of quantum fluctuations and the excitation spectrum for the antiferromagnetic Heisenberg model on a two-dimensional quasicrystal, by numerically solving linear spin-wave theory on finite approximants of the octagonal tiling. Previous quantum Monte Carlo results for the distribution of local staggered magnetic moments and the static spin structure factor are reproduced well within this approximate scheme. Furthermore, the magnetic excitation spectrum consists of magnonlike low-energy modes, as well as dispersionless high-energy states of multifractal nature. The dynamical spin structure factor, accessible to inelastic neutron scattering, exhibits linear-soft modes at low energies, self-similar structures with bifurcations emerging at intermediate energies, and flat bands in high-energy regions. We find that the distribution of local staggered moments stemming from the inhomogeneity of the quasiperiodic structure leads to a characteristic energy spread in the local dynamical spin susceptibility, implying distinct nuclear magnetic resonance spectra, specific for different local environments.