Bera Arabinda, Zaccone Alessio, Baggioli Matteo
Department of Physics "A. Pontremoli", University of Milan, Milan, Italy.
Wilczek Quantum Center, School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai, China.
Nat Commun. 2025 Jul 1;16(1):5990. doi: 10.1038/s41467-025-61103-7.
The underlying structural disorder renders the concept of topological defects in amorphous solids difficult to apply and hinders a first-principle identification of the microscopic carriers of plasticity and of regions prone to structural rearrangements ("soft spots"). Recently, it has been proposed that well-defined topological defects can still be identified in glasses. However, all existing proposals apply only to two spatial dimensions and are correlated with plasticity. We propose that hedgehog topological defects can be used to characterize plasticity in 3D glasses and to geometrically identify soft spots. We corroborate this idea via simulations of a Kremer-Grest 3D polymer glass, analyzing both the normal mode eigenvector field and the displacement field around large plastic events. Unlike the 2D case, the sign of the topological charge in 3D within the eigenvector field is ambiguous, and the defect geometry plays a crucial role. We find that topological hedgehog defects relevant for plasticity exhibit hyperbolic geometry, resembling 2D anti-vortices having negative winding number. Our results confirm the feasibility of a topological characterization of plasticity in 3D glasses, revealing an intricate interplay between topology and geometry that is absent in 2D disordered systems.
潜在的结构无序使得非晶态固体中的拓扑缺陷概念难以应用，并阻碍了对塑性微观载体以及易于发生结构重排区域（“软点”）的第一性原理识别。最近，有人提出在玻璃中仍可识别出定义明确的拓扑缺陷。然而，所有现有的提议仅适用于二维空间，且与塑性相关。我们提出刺猬拓扑缺陷可用于表征三维玻璃中的塑性，并从几何角度识别软点。我们通过对Kremer-Grest三维聚合物玻璃的模拟来证实这一想法，分析了大塑性事件周围的正则模本征向量场和位移场。与二维情况不同，本征向量场中三维拓扑电荷的符号不明确，缺陷几何形状起着关键作用。我们发现与塑性相关的拓扑刺猬缺陷呈现双曲线几何形状，类似于具有负缠绕数的二维反涡旋。我们的结果证实了对三维玻璃中的塑性进行拓扑表征的可行性，揭示了二维无序系统中不存在的拓扑与几何之间的复杂相互作用。
