该研究团队深入探索了单轴稀土铁磁体在量子世界深处的动力学特性。他们发现，畴壁运动及相关滞后现象是由量子成核触发的，随后演化成大规模的畴壁运动，这呈现出一种特殊的巴克豪森噪声形式。研究人员观察到，雪崩动力学中的非临界行为已超越了传统的重整化群方法和经典畴壁模型的解释范畴。
进一步的研究揭示，这种“量子巴克豪森噪声”展现出两种截然不同的畴壁运动机制，两者均源于量子力学，但对横向施加于自旋（伊辛）轴的外部磁场的依赖性截然不同。这些观察结果可以通过畴壁对的关联运动来解读，这些畴壁对由近邻片（畴壁的部分）的共隧穿成核形成，并通过偶极相互作用相互关联；而这种关联性在横向场的作用下会受到抑制。研究人员推测，类似的宏观关联性可能也会在其他具有长程相互作用的系统的滞后现象中出现。
附：英文原文
Title: Quantum Barkhausen noise induced by domain wall cotunneling
Author: Simon, C., Silevitch, D.M., Stamp, P.C.E., Rosenbaum, T.F.
Issue&Volume: 2024-3-19
Abstract: Most macroscopic magnetic phenomena (including magnetic hysteresis) are typically understood classically. Here, we examine the dynamics of a uniaxial rare-earth ferromagnet deep within the quantum regime, so that domain wall motion, and the associated hysteresis, is initiated by quantum nucleation, which then grows into large-scale domain wall motion, which is observable as an unusual form of Barkhausen noise. We observe noncritical behavior in the resulting avalanche dynamics that only can be explained by going beyond traditional renormalization group methods or classical domain wall models. We find that this “quantum Barkhausen noise” exhibits two distinct mechanisms for domain wall movement, each of which is quantum-mechanical, but with very different dependences on an external magnetic field applied transverse to the spin (Ising) axis. These observations can be understood in terms of the correlated motion of pairs of domain walls, nucleated by cotunneling of plaquettes (sections of domain wall), with plaquette pairs correlated by dipolar interactions; this correlation is suppressed by the transverse field. Similar macroscopic correlations may be expected to appear in the hysteresis of other systems with long-range interactions.
DOI: 10.1073/pnas.2315598121
Source: https://www.pnas.org/doi/abs/10.1073/pnas.2315598121