标题： 拓扑增强的超导性：菱形石墨烯的可能影响 显示英文标题

标题： Topologically enabled superconductivity: possible implications for rhombohedral graphene

摘要： 我们提出了一种拓扑机制，用于解释从陈-2绝缘体中出现的超导性。 尽管直观上认为时间反演对称性破缺会阻止超导性，但事实恰恰相反：对于广义的吸引-U哈德纳-哈伯德模型的显式模型计算表明，超导性仅在量子反常霍尔态附近稳定，而不在平凡的时间反演对称带绝缘体附近稳定。 由于标准的巴丁-库珀-施里弗类似平均场理论无法捕捉任何超导态，我们通过一种涉及费米子电荷子、玻色子色子和涌现U(1)规范场的有效分数量场论来解释这一现象。 当电荷子形成一个具有能隙的拓扑能带结构时，该规范场的单个磁单极子的增殖被禁止。 然而，长程的磁单极子-反磁单极子相关性出现，我们认为这些对应于超导序。 在广泛的孤子转子平均场计算的基础上使用随机相位近似，我们表征了超导体的相干长度和刚度。 由此，我们推导出参数空间中的相图，并进一步讨论了掺杂、温度和外加磁场的影响。 我们通过使用有效自旋模型和古茨维勒投影波函数的计算来补充分数量理论。 虽然主要基于一个简单的玩具模型，但我们认为我们的发现有助于更好地理解在邻近量子反常霍尔绝缘体的参数区域内，自旋和谷极化的菱形石墨烯多层结构中出现的超导性。 显示英文摘要

摘要： We present a topological mechanism for superconductivity emerging from Chern-2 insulators. While, naively, time-reversal symmetry breaking is expected to prevent superconductivity, it turns out that the opposite is the case: An explicit model calculation for a generalized attractive-U Haldane-Hubbard model demonstrates that superconductivity is only stabilized near the quantum anomalous Hall state, but not near a trivial, time-reversal symmetric band insulator. As standard Bardeen-Cooper-Schrieffer-like mean-field theory fails to capture any superconducting state, we explain this using an effective fractionalized field theory involving fermionic chargeons, bosonic colorons and an emergent U(1) gauge field. When the chargeons form a gapped topological band structure, the proliferation of single monopoles of this gauge field is forbidden. However, long-ranged monopole-antimonopole correlations emerge, and we argue that those correspond to superconducting order. Using random phase approximation on top of extensive slave-rotor mean-field calculations we characterize coherence length and stiffness of the superconductor. Thereby, we deduce the phase diagram in parameter space and furthermore discuss the effect of doping, temperature and an external magnetic field. We complement the fractionalized theory with calculations using an effective spin model and Gutzwiller projected wavefunctions. While mostly based on a simple toy model, we argue that our findings contribute to a better understanding of superconductivity emerging out of spin- and valley polarized rhombohedral graphene multilayers in a parameter regime with nearby quantum anomalous Hall insulators.