High-Angular-Momentum Topological Superconductivity in the Largest-Angle Twisted Homo-bilayer Systems
Yu-Bo Liu, Yongyou Zhang, Wei-Qiang Chen, Fan Yang
备注：
4.2 pages, 3 figures, with Supplementary Materials. This is the generalized version of arXiv:2106.08542. In the old version, we only consider a special example, here we give a general theory
We study the largest-angle twisted homo-bilayer (LA-THB) systems, hosting Moiréless quasi-crystal (QC) structure. We propose to use these materials to generate high-angular-momentum (HAM) topological superconductivities (TSCs) protected by their QC symmetries absent on conventional crystalline materials. This proposal is based on our universal Ginzburg-Landau theory based analysis which yields the general conclusion that, when each $D_n$-symmetric ($n$ is even) monolayer hosts SC with pairing angular momentum $l\le \frac{n}{2}$, the interlayer Josephson coupling will induce SC with pairing angular momentum $L=l$ or $L=n-l$ in the LA-THB, determined by microscopic details. The latter one is just the HAM TSC if $l>0$. Based on our revised perturbational-band theory, we develop general microscopic framework to study the QC LA-THBs involving electron-electron interactions, adopting which we study three examples, i.e. the 30$^\circ$- twisted bilayer graphene, the 30$^\circ$- twisted bilayer BC$_3$, and the 45$^\circ$- twisted bilayer cuprates. The $g+ig$- $h+ih$- and $d+id$- TSCs with HAM $L=4,5$ and $2$ can emerge in certain doping regimes in these systems, respectively.
Vortical versus skyrmionic states in the topological phase of a twisted bilayer with $d$-wave superconducting pairing
最近的研究表明，当超导体Bi $_2$ Sr $_2$ CaCu $_2$ O $_{8+δ}$的两个扭曲单层在一定的扭曲角下发生耦合时，会出现手性拓扑相.在这项工作中，我们揭示了这种扭曲的超导双层膜的行为与$d_{x^2-y^2}$配对对称的存在下施加磁场。具体来说，我们表明，紧急涡旋物质可以作为吸烟枪检测拓扑超导在这样的双层。此外，我们报告了两个不同的skyrmionic状态，表征手性拓扑相位，并提供充分的考虑他们的实验签名和他们的演变与扭曲角。
