近日，英国剑桥大学Jonathan N. Hallén及其研究小组研究了干净磁晶体中的动态分形和异常噪声。该项研究成果发表在2022年12月16日出版的《科学》上。
在这项工作中，课题组在热力学平衡的无序、化学计量和三维磁晶体中发现了一个涌现的动力学分形。这一现象源于对自旋冰中磁单极激发的动力学的约束，它限制了它们在分形上的移动。这一观测解释了自旋冰化合物Dy2Ti2O7磁噪声实验中发现的异常指数，并解决了关于其快速发散弛豫时间的长期难题。自旋冰能够表现出如此显著的现象，这表明在简单拓扑多体系统的合作动力学中还会有更多意想不到的发现。
研究人员表示，分形--具有非整数维度的物体--在自然界的流形环境和长度尺度中出现。
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附：英文原文
Title: Dynamical fractal and anomalous noise in a clean magnetic crystal
Author: Jonathan N. Hallén, Santiago A. Grigera, D. Alan Tennant, Claudio Castelnovo, Roderich Moessner
Issue&Volume: 2022-12-16
Abstract: Fractals—objects with noninteger dimensions—occur in manifold settings and length scales in nature. In this work, we identify an emergent dynamical fractal in a disorder-free, stoichiometric, and three-dimensional magnetic crystal in thermodynamic equilibrium. The phenomenon is born from constraints on the dynamics of the magnetic monopole excitations in spin ice, which restrict them to move on the fractal. This observation explains the anomalous exponent found in magnetic noise experiments in the spin ice compound Dy2Ti2O7, and it resolves a long-standing puzzle about its rapidly diverging relaxation time. The capacity of spin ice to exhibit such notable phenomena suggests that there will be further unexpected discoveries in the cooperative dynamics of even simple topological many-body systems.
DOI: add1644
Source: https://www.science.org/doi/10.1126/science.add1644
来源：科学网 小柯机器人
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