弱无序二维海森堡铁磁体中自旋刚度的消失
Vanishing spin stiffness in weakly disordered two-dimensional Heisenberg ferromagnets
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中文总结 AI 辅助
研究弱无序二维海森堡铁磁体，通过复本场论计算和数值对角化发现，少量反铁磁键改变长波动力学，有效无序强度粗粒化下增长，自旋刚度降低，产生异常软磁振子，流动趋向无限无序、零刚度状态。
中文摘要 AI 辅助
我们表明，一小部分反铁磁键定性地改变了二维海森堡铁磁体的长波动力学。尽管经典基态仍被磁化，但弱键挫折会产生局部自旋刚度的对数相关空间涨落，尽管微观无序是短程的。复本场论计算表明，有效无序强度在粗粒化下增长，而自旋刚度降低，产生具有尺度依赖动力学指数\(z>2\)的异常软磁振子。半经典自旋波哈密顿量的数值对角化证实了异常低能标度。流动趋向于无限无序、零刚度状态。
英文摘要
We show that a small fraction of antiferromagnetic bonds qualitatively alters the long-wavelength dynamics of two-dimensional Heisenberg ferromagnets. Although the classical ground state remains magnetized, weak bond frustration generates logarithmically correlated spatial fluctuations of the local spin stiffness, despite the microscopic disorder being short ranged. A replica field theory calculation shows that the effective disorder strength grows under coarse graining, while the spin stiffness decreases, yielding anomalously soft magnons with a scale-dependent dynamical exponent $z > 2$. Numerical diagonalization of the semiclassical spin-wave Hamiltonian confirms the anomalous low-energy scaling. The flow is toward an infinite-disorder, zero stiffness regime.
