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arXiv 1809.07799cond-mat.stat-mech
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三维海森堡反铁磁体的非普适临界老化标度

Non-universal critical aging scaling in three-dimensional Heisenberg antiferromagnets

Riya Nandi, Uwe C. Täuber

摘要:

我们数值研究了三维各向同性海森堡反铁磁体的稳态和非平衡临界动力学。由于非保守的交错磁化耦合动态的保守磁化密度,我们采用了一种混合模拟算法,结合可逆的自旋进动与弛豫川崎自旋交换过程。我们测量的动态临界指数,并确定一个合适的中间时间窗口,以获得老化标度指数。我们的研究结果支持早期的重整化群预测:虽然临界老化崩溃指数假设一个普遍的值,相关的时间衰减指数在两个时间自旋自相关函数依赖于守恒场的初始分布,在这里,特别是对初始自旋取向分布的宽度。

英文摘要:

We numerically investigate the stationary and non-equilibrium critical dynamics in three-dimensional isotropic Heisenberg antiferromagnets. Since the non-conserved staggered magnetization couples dynamically to the conserved magnetization density, we employ a hybrid simulation algorithm that combines reversible spin precession with relaxational Kawasaki spin exchange processes. We measure the dynamic critical exponent and identify a suitable intermediate time window to obtain the aging scaling exponents. Our results support an earlier renormalization group prediction: While the critical aging collapse exponent assumes a universal value, the associated temporal decay exponent in the two-time spin autocorrelation function depends on the initial distribution of the conserved fields; here, specifically on the width of the initial spin orientation distribution.

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