The crystal structure of a material creates a periodic potential that electrons move through giving rise to the electronic band structure of the material. When two-dimensional materials are stacked, the twist angle between the layers becomes an additional degree freedom for the resulting heterostructure. As this angle changes, the electronic band structure is modified leading to the possibility of flat bands with localized states and enhanced electronic correlations1–6. In transition metal dichalcogenides, flat bands have been theoretically predicted to occur over a range of twist angles below ~7 degrees4. Here we show the existence of a flat band in the electronic structure of a 3° twisted bilayer WSe2 sample using scanning tunneling spectroscopy. Direct spatial mapping of wavefunctions at the flat band energy have shown that the flat band is localized in the form of a hexagonal network in excellent agreement with first-principle density functional theory calculations4.
|Original language||English (US)|
|State||Published - Oct 28 2019|
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