Flat-band materials such as the kagome metals or moiré superlattices are of intense current interest. Flat bands can result from the electron motion on numerous (special) lattices and usually exhibit topological properties. Their reduced bandwidth proportionally enhances the effect of Coulomb interaction, even when the absolute magnitude of the latter is relatively small. Seemingly unrelated to these materials is the large family of strongly correlated electron systems, which include the heavy-fermion compounds, and cuprate and pnictide superconductors. In addition to itinerant electrons from large, strongly overlapping orbitals, they frequently contain electrons from more localized orbitals, which are subject to a large Coulomb interaction. The question then arises as to what commonality in the physical properties and microscopic physics, if any, exists between these two broad categories of materials. A rapidly increasing body of strikingly similar phenomena across the different platforms — from electronic localization–delocalization transitions to strange-metal behaviour and unconventional superconductivity — suggests that similar underlying principles could be at play. Indeed, it has recently been suggested that flat-band physics can be understood in terms of Kondo physics. Inversely, the concept of electronic topology from lattice symmetry, which is fundamental in flat-band systems, is enriching the field of strongly correlated electron systems, in which correlation-driven topological phases are increasingly being investigated. In this Perspective article, we elucidate this connection, survey the new opportunities for cross-fertilization across platforms and assess the prospect for new insights that may be gained into correlation physics and its intersection with electronic topology.

诸如戈薇金属或莫尔超晶格之类的平带材料目前引起了人们的强烈兴趣。平带可以由许多（特殊）晶格上的电子运动产生，并且通常表现出拓扑特性。它们减小的带宽成比例地增强了库仑相互作用的效果，即使后者的绝对量值相对较小。看似与这些材料无关的是强相关电子系统大家族，其中包括重费米子化合物、铜酸盐和磷化物超导体。除了来自大的、强烈重叠的轨道的巡回电子之外，它们还经常包含来自更局域化轨道的电子，这些电子受到大的库仑相互作用的影响。接下来的问题是，这两大类材料之间在物理特性和微观物理方面存在哪些共同点（如果有的话）。不同平台上迅速增加的惊人相似的现象——从电子局域化-离域转变到奇异金属行为和非常规超导——表明类似的基本原理可能在发挥作用。事实上，最近有人提出可以用近藤物理学来理解平带物理学。相反，来自晶格对称的电子拓扑概念是平带系统的基础，它正在丰富强相关电子系统的领域，其中相关驱动的拓扑相越来越受到研究。在这篇《观点》文章中，我们阐明了这种联系，调查了跨平台交叉融合的新机会，并评估了相关物理及其与电子拓扑交叉方面可能获得的新见解的前景。