扭曲三维结构中由 Umklapp 散射产生的无自旋拓扑手性
Spinless topological chirality from Umklapp scattering in twisted 3D structures
AI总结：
本文在两类扭曲三维石墨结构中，发现仅由结构手性即可产生无自旋拓扑手性，包括手性 Weyl 半金属相和具有手性棱态的更高阶 Dirac 半金属，并揭示其机制为谷间 Umklapp 散射引入的 π 通量 Z2 晶格规范场。
摘要：
与有自旋系统相比，无自旋系统因其独特的代数结构而表现出独特的拓扑特性。由于通常与自旋相关的手性相互作用缺失，拓扑手性与结构手性之间可能存在一种有趣但尚未被探索的相互作用。在此，我们发现无自旋拓扑手性可以完全来源于结构手性，即来源于无结构单元的三维空间排布模式，并以两类扭曲石墨系统为例进行了说明。在一个并非在所有方向都具有周期性的三维螺旋扭曲结构中，我们发现了一种手性 Weyl 半金属相，其中体拓扑和手性表面态均由螺旋方向决定。而在一个由层间交替扭曲角符号形成的三维周期结构中，发现了一种具有手性棱态的更高阶 Dirac 半金属。这些新颖拓扑态的背后是谷间 Umklapp 散射，它捕捉了扭曲界面的手性，有效地导致符号翻转的手性层间跃迁，从而引入了改变对称代数的 π 通量 Z2 晶格规范场。我们的发现指出了一条通过图案化排列无特征单元的扭曲阵列来工程化拓扑手性的新途径，这可以拓展拓扑光子学和拓扑声学的设计原理。
英文摘要：
Spinless systems exhibit unique topological characteristics compared to spinful ones, stemming from their distinct algebra. Without chiral interactions typically linked to spin, an intriguing yet unexplored interplay between topological and structural chirality may be anticipated. Here we discover spinless topological chiralities solely from structural chiralities that lie in the 3D spatial patterning of structureless units, exemplified using two types of twisted graphite systems. In a 3D screw twisted structure without periodicity in all directions, we find a chiral Weyl semimetal phase where bulk topology and chiral surface states are both determined by the screw direction. And in a 3D periodic structure formed with layer-alternating twist angle signs, a higher-order Dirac semimetal with chiral hinge states is discovered. Underlying these novel topological states is the intervalley Umklapp scattering that captures the chirality of the twisted interfaces, leading effectively to a sign-flipped chiral interlayer hopping, thereby introducing $π$-flux Z2 lattice gauge field that alters the symmetry algebra. Our findings point to a new pathway for engineering topological chirality through patterning twisted arrays of featureless units, which can expand the design principles for topological photonics and acoustics.
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