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arXiv 2210.08736cond-mat.mes-hallcond-mat.mtrl-sciphysics.comp-ph
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表面轨道磁化理论

Towards a theory of surface orbital magnetization

Daniel Seleznev, David Vanderbilt

摘要:

体轨道磁化理论在倒易空间中基于Berry曲率和相关量,在实空间中根据量子力学局域标记的空间平均来制定。在这里,我们考虑一个三维的反铁磁材料具有消失的体积,但非零的表面轨道磁化。我们问是否表面磁化的表面法向分量是很好地定义,如果是这样的话,如何计算它。作为对应于这个量的物理观测量,我们确定了宏观电流沿铰链由两个方面共享。然而,铰链电流仅约束相邻刻面上的表面磁化强度的差异,留下潜在的模糊性。通过进行对称性分析,我们发现,只有晶体表现出赝标量对称承认定义明确的磁化在其表面的经典水平。然后,我们探讨了通过应用于量子局部标记的粗粒化过程计算表面磁化的可能性。我们表明,多个表达式的本地标记存在,并施加限制,筛选出潜在的有意义的候选人。使用几个紧束缚模型作为我们的理论测试床和几个潜在的标记,我们计算表面磁化板的几何形状和比较他们的预测与明确计算的宏观铰链电流棒的几何形状。我们发现,只有一个特定形式的标记始终预测正确的铰链电流。

英文摘要:

The theory of bulk orbital magnetization has been formulated both in reciprocal space based on Berry curvature and related quantities, and in real space in terms of the spatial average of a quantum mechanical local marker. Here we consider a three-dimensional antiferromagnetic material having a vanishing bulk but a nonzero surface orbital magnetization. We ask whether the surface-normal component of the surface magnetization is well defined, and if so, how to compute it. As the physical observable corresponding to this quantity, we identify the macroscopic current running along a hinge shared by two facets. However, the hinge current only constrains the difference of the surface magnetizations on the adjoined facets, leaving a potential ambiguity. By performing a symmetry analysis, we find that only crystals exhibiting a pseudoscalar symmetry admit well-defined magnetizations at their surfaces at the classical level. We then explore the possibility of computing surface magnetization via a coarse-graining procedure applied to a quantum local marker. We show that multiple expressions for the local marker exist, and apply constraints to filter out potentially meaningful candidates. Using several tight-binding models as our theoretical test bed and several potential markers, we compute surface magnetizations for slab geometries and compare their predictions with explicit calculations of the macroscopic hinge currents of rod geometries. We find that only a particular form of the marker consistently predicts the correct hinge currents.

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