时空晶体的射影时空对称性

Spinful topological phases in acoustic crystals with projective PT symmetry

For the classification of topological phases of matter, an important consideration is whether a system is spinless or spinful, as these two classes have distinct symmetry algebra that gives rise to fundamentally different topological phases. However, only recently has it been realized theoretically that in the presence of gauge symmetry, the algebraic structure of symmetries can be projectively represented, which possibly enables the switch between spinless and spinful topological phases. Here, we report the first experimental demonstration of this idea by realizing spinful topological phases …

Topological non-symmorphic crystalline insulators

In this work, we identify a new class of Z2 topological insulator protected by non-symmorphic crystalline symmetry, dubbed a "topological non-symmorphic crystalline insulator". We construct a concrete tight-binding model with the non-symmorphic space group pmg and confirm the topological nature of this model by calculating topological surface states and defining a Z2 topological invariant. Based on the projective representation theory, we extend our discussion to other non-symmorphic space groups that allows to host topological non-symmorphic crystalline insulators.

利用时空超材料实现合成晶体旋转

Synthetic crystal rotation with spacetime metamaterials

本文提出利用时空超材料实现合成晶体旋转，突破传统旋转频率限制，揭示了光与旋转体相互作用中能量与自旋角动量守恒的新机制。

非传统自旋磁性在准晶中的表现：超空间投影构造

Unconventional Altermagnetism in Quasicrystals: A Hyperspatial Projective Construction

本文通过超空间投影构造准晶格，揭示了非传统g-波和h-波自旋磁性，拓展了自旋磁性研究的范围。

Kronecker products of projective representations of translation groups

Projective irreps of (Z_N)^2 can be labelled by divisors n of N. A product of two irreps, labelled by n and n', can be decomposed into projective irreps labelled by M, where M strongly depends on the arithmetic structure of N, n, n' and their relations (gcd, lcm etc.). Such decompostion describes two important physical effects: (i) changes of a magnetic period of the crystal lattice (with unchaged crystal period N); (2) each representation can be related with a charged particle moving in an external magnetic field and a periodic potential --- a product of (projective) irreps corresponds to int…

Hofstadter 拓扑与实空间不变量及重入投影对称性

Hofstadter Topology with Real Space Invariants and Reentrant Projective Symmetries

本文提出实空间不变量分类Hofstadter拓扑相，揭示磁通诱导的投影点群重入机制，并以Schur乘子预测零磁通拓扑的Hofstadter响应。

通量Su-Schrieffer-Heeger模型中由投影对称性决定的拓扑

Projective symmetry determined topology in flux Su-Schrieffer-Heeger model

本文提出通量SSH模型，证明一维系统的Zak相位可完全由投影对称代数决定，并通过电路阵列实验验证，为设计拓扑晶体提供了新途径。

投影镜像陈绝缘体的声学实现

Acoustic realization of projective mirror Chern insulators

本文通过声学实验实现了投影镜像陈绝缘体，提出构建投影镜像对称性的通用方法，并直接测量了非阿贝尔贝里曲率与镜像陈数，证实了该拓扑相的存在。

Switching spinless and spinful topological phases with projective $PT$ symmetry

A fundamental dichotomous classification for all physical systems is according to whether they are spinless or spinful. This is especially crucial for the study of symmetry-protected topological phases, as the two classes have distinct symmetry algebra. As a prominent example, the spacetime inversion symmetry $PT$ satisfies $(PT)^2=\pm 1$ for spinless/spinful systems, and each class features unique topological phases. Here, we reveal a possibility to switch the two fundamental classes via $\mathbb{Z}_2$ projective representations. For $PT$ symmetry, this occurs when $P$ inverses the gauge tran…

配对对称性与费米子投影对称群

Pairing Symmetry and Fermion Projective Symmetry Groups

本文提出用投影对称群描述超导费米子激发对称性，建立其与配对对称性的对应，枚举32个点群情形，并展示其对拓扑超导分类的指导意义。