Moiré superlattices in van der Waals heterostructures provide a tunable platform to study emergent properties that are absent in the natural crystal form. Twisted bilayer transition metal dichalcogenides (TB-TMDs) can host moiré flat bands over a wide range of twist angles. For twist angle close to 60°, it was predicted that TB-TMDs undergo a lattice reconstruction which causes the formation of ultra-flat bands. Here, by using scanning tunneling microscopy and spectroscopy, we show the emergence of multiple ultra-flat bands in twisted bilayer WSe₂ when the twist angle is within 3° of 60°. The ultra-flat bands are manifested as narrow tunneling conductance peaks with estimated bandwidth less than 10 meV, which is only a fraction of the estimated on-site Coulomb repulsion energy. The number of these ultra-flat bands and spatial distribution of the wavefunctions match well with the theoretical predictions, strongly evidencing that the observed ultra-flat bands are induced by lattice reconstruction. Our work provides a foundation for further study of the exotic correlated phases in TB-TMDs.

范德瓦尔斯异质结构中的莫尔超晶格为研究天然晶体形式中不存在的涌现性质提供了一个可调平台。扭曲的双层过渡金属二硫属化物 (TB-TMD) 可以在很宽的扭曲角范围内形成莫尔平带。对于接近 60° 的扭曲角，预计 TB-TMD 会经历晶格重构，从而导致超平坦带的形成。在这里，通过使用扫描隧道显微镜和光谱学，我们展示了扭曲双层 WSe ₂中多个超平坦带的出现当扭转角在 60° 的 3° 以内时。超平坦带表现为窄隧道电导峰，估计带宽小于 10 meV，这只是估计的现场库仑排斥能的一小部分。这些超平坦带的数量和波函数的空间分布与理论预测非常吻合，有力地证明了观察到的超平坦带是由晶格重建引起的。我们的工作为进一步研究 TB-TMD 中奇异的相关相提供了基础。