Electronic states in quasicrystals generally preclude a Bloch description¹, rendering them fascinating and enigmatic. Owing to their complexity and scarcity, quasicrystals are underexplored relative to periodic and amorphous structures. Here we introduce a new type of highly tunable quasicrystal easily assembled from periodic components. By twisting three layers of graphene with two different twist angles, we form two mutually incommensurate moiré patterns. In contrast to many common atomic-scale quasicrystals^2,3, the quasiperiodicity in our system is defined on moiré length scales of several nanometres. This ‘moiré quasicrystal’ allows us to tune the chemical potential and thus the electronic system between a periodic-like regime at low energies and a strongly quasiperiodic regime at higher energies, the latter hosting a large density of weakly dispersing states. Notably, in the quasiperiodic regime, we observe superconductivity near a flavour-symmetry-breaking phase transition^4,5, the latter indicative of the important role that electronic interactions play in that regime. The prevalence of interacting phenomena in future systems with in situ tunability is not only useful for the study of quasiperiodic systems but may also provide insights into electronic ordering in related periodic moiré crystals^{6,7,8,9,10,11,12}. We anticipate that extending this platform to engineer quasicrystals by varying the number of layers and twist angles, and by using different two-dimensional components, will lead to a new family of quantum materials to investigate the properties of strongly interacting quasicrystals.

准晶体中的电子态通常无法进行布洛赫描述¹，这使得它们令人着迷且神秘。由于准晶的复杂性和稀缺性，相对于周期性和非晶结构，准晶的研究还不够充分。在这里，我们介绍一种新型的高度可调谐准晶体，可以轻松地由周期性组件组装而成。通过以两种不同的扭转角度扭转三层石墨烯，我们形成了两种互不相称的莫尔图案。与许多常见的原子级准晶体^2,3相比，我们系统中的准周期性是在几纳米的莫尔长度尺度上定义的。这种“莫尔准晶体”使我们能够在低能量的类周期状态和高能量的强准周期状态之间调节化学势，从而调节电子系统，后者具有大密度的弱色散态。值得注意的是，在准周期状态下，我们在味道对称性破坏相变附近观察到超导性^4,5，后者表明电子相互作用在该状态下发挥着重要作用。具有原位可调谐性的未来系统中相互作用现象的普遍存在不仅对于准周期系统的研究有用，而且还可以为相关周期性莫尔晶体中的电子排序提供见解^{6,7,8,9,10,11,12}。我们预计，通过改变层数和扭转角以及使用不同的二维组件，将该平台扩展到设计准晶体，将产生一个新的量子材料系列，以研究强相互作用准晶体的特性。