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arXiv 2106.08520cond-mat.softcond-mat.mes-hall
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共形晶体中的缺陷:离散与连续向错模型

Defects in Conformal Crystals: Discrete vs. Continuous Disclination Models

Qingyou Meng, Gregory M. Grason

摘要:

在排斥模型中研究了拓扑缺陷的形成与基态填充的关系。具体来说,我们考虑了屏蔽的2D库仑排斥,它可以方便地参数化相互作用范围的影响,但也可以作为II型超导体中聚电解质丝或涡旋的受限平行阵列的简单物理模型。排斥和限制,分别扩散和集中的粒子密度的抵消趋势,导致集群中的非均匀密度的精力充沛的偏好。在这样的系统中的基态先前被建模为{ \it保形晶体},其由局部等三角形填充组成,其局部面密度表现出长程梯度。在这里,我们评估两个理论模型,连接的偏好不均匀的密度形成的向错缺陷,其中一个假设一个连续分布的缺陷,而第二个考虑的量化和局部性质的向错在六角共形晶体。将这两种模型与离散粒子团的数值模拟进行比较,研究了相互作用范围和束缚势对基态缺陷的影响。我们发现,治疗向错连续分布以及捕获的基态中的长程相互作用的制度的拓扑缺陷的数量,而相互作用变得更短的范围内,它大大高估了总缺陷电荷的增长。对离散缺陷理论的分析表明,连续缺陷理论的局限性可归因于共形晶体基态中正负向错位置的不对称性,以及向错自能对拓扑电荷符号的强烈不对称依赖性。

英文摘要:

We study the relationship between topological defect formation and ground-state packings in a model of repulsions in external confining potentials. Specifically we consider screened 2D Coulombic repulsions, which conveniently parameterizes the effects of interaction range, but also serves as simple physical model of confined, parallel arrays of polyelectrolyte filaments or vortices in type-II superconductors. The countervailing tendencies of repulsions and confinement to, respectively, spread and concentrate particle density leads to an energetic preference for non-uniform densities in the clusters. Ground states in such systems have previously been modeled as {\it conformal crystals}, which are composed of locally equitriangular packings whose local areal densities exhibit long range gradients. Here, we assess two theoretical models that connect the preference for non-uniform density to the formation of disclination defects, one of which assumes a continuum distributions of defect, while the second considers the quantized and localized nature of disclinations in hexagonal conformal crystals. Comparing both models to numerical simulations of discrete particles clusters, we study the influence of interaction range and confining potential on defects in ground states. We show that treating disclinations as continuously distributable well-captures the number of topological defects in the ground state in the regime of long-range interactions, while as interactions become shorter range, it dramatically overpredicts the to growth in total defect charge. Analysis of the discretized defect theory suggests that limitations of the continuous defect theory can be attributed to the asymmetry in the placement of positive vs. negative disclinations in the conformal crystal ground states, as well as a strongly asymmetric dependence of self-energy of disclinations on sign of topological charge.

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