标题： Kagome晶格上环电流Chern金属的旋转超导性 显示英文标题

标题： Roton Superconductivity from Loop-Current Chern Metal on the Kagome Lattice

摘要： 受非磁性kagome金属AV₃Sb₅中时间反演对称性（TRS）破缺证据的启发，人们提出了一个关于观测到的电荷密度波（CDW）态的新颖电子序——持久轨道环电流（LC）。这种LC序及其对随后超导（SC）态的影响是kagome材料新物理的核心。 我们表明，LC序从根本上改变了配对不稳定性及超导态，从而导致了一种非凡的拓扑超导体，被称为“旋子超导体”。 在kagome晶格上的单轨道模型中，LC-CDW态在van Hove填充附近是一种Chern金属，具有部分填充的Chern带，该带包含3个Chern费米口袋（CFPs）。CFP上的准粒子配对产生了3个由TRS破缺LC诱导的复杂约瑟夫森耦合所耦合的超导组分。由于与三重旋转和平面置换相关的离散量子几何特性，微小的LC会产生较大的约瑟夫森相位，驱动主要的超导不稳定性成为旋子超导体，在其中3个超导组分的相对相位被锁定在120°，形成具有配对密度调制的新兴漩涡-反漩涡晶格。 旋子超导体的性质包括携带非零电流传导的拓扑手性边缘态、分数1/3漩涡激发和抗内部手性相涨落的电荷6e库珀对三重态。我们将这些超导性质与最近关于kagome超导体中TRS破缺手性超导态的实验证据联系起来，该证据展示了配对密度调制、零场超导二极管效应和电荷6e通量量子化。 这些发现也适用于其他系统中由轨道驱动的量子异常霍尔态与超导态之间的相互作用，例如基于石墨烯和过渡金属二硫属化物的量子材料。 显示英文摘要

摘要： Motivated by the evidence for time-reversal symmetry (TRS) breaking in nonmagnetic kagome metals AV3Sb5, a novel electronic order of persistent orbital loop-current (LC) has been proposed for the observed charge density wave (CDW) state. The LC order and its impact on the succeeding superconducting (SC) state are central to the new physics of the kagome materials. We show that the LC order fundamentally changes the pairing instability and the SC state, leading to an extraordinary topological superconductor, dubbed as a roton superconductor. In the single-orbital model on the kagome lattice, the LC-CDW state is a Chern metal near van Hove filling with a partially filled Chern band hosting 3 Chern Fermi pockets (CFPs). Cooper pairing of quasiparticles on the CFPs generates 3 SC components coupled by complex Josephson couplings induced by the TRS breaking LC. Due to the discrete quantum geometry associated with the 3-fold rotation and sublattice permutation, a small LC produces a large Josephson phase that drives the leading SC instability to the roton superconductor where the relative phases of the 3 SC components are locked at 120°, forming an emergent vortex-antivortex lattice with pair density modulations. Properties of the roton superconductor include topological chiral edge states carrying nonzero electric currents, fractional 1/3 vortex excitations and charge-6e Cooper pair triplets that are immune to the internal chiral phase fluctuations. We discuss these SC properties in connection to recent experimental evidence for TRS breaking chiral SC state in kagome superconductors, exhibiting pair density modulations, zero-field SC diode effect, and charge-6e flux quantization. These findings are also relevant for the interplay between the orbital-driven quantum anomalous Hall and SC states in other systems, e.g. the graphene and transition metal dichalcogenide based quantum materials.