Observation of flat Γ moiré bands in twisted bilayer WSe2

I provided the theory for a wonderful ARPES experiment that revealed the presence of flat bands in twisted bilayer WSe2. To our surprise, we only saw the flat bands around Γ and not at K — where they were to be expected based on all other (transport, exciton, STM) experiments. So some new mysteries to solve! Now available on the arXiv:

Title: Observation of flat Γ moiré bands in twisted bilayer WSe2
Reference: arXiv:2211.01192
Gianmarco Gatti, Julia Issing, Louk Rademaker, Florian Margot, Tobias A. de Jong, Sense Jan van der Molen, Jérémie Teyssier, Timur K. Kim, Matthew D. Watson, Cephise Cacho, Pavel Dudin, José Avila, Kumara Cordero Edwards, Patrycja Paruch, Nicolas Ubrig, Ignacio Gutiérrez-Lezama, Alberto Morpurgo, Anna Tamai, Felix Baumberger
The recent observation of correlated phases in transition metal dichalcogenide moiré systems at integer and fractional filling promises new insight into metal-insulator transitions and the unusual states of matter that can emerge near such transitions. Here, we combine real- and momentum-space mapping techniques to study moiré superlattice effects in 57.4∘ twisted WSe2 (tWSe2). Our data reveal a split-off flat band that derives from the monolayer Γ states. Using advanced data analysis, we directly quantify the moiré potential from our data. We further demonstrate that the global valence band maximum in tWSe2 is close in energy to this flat band but derives from the monolayer K-states which show weaker superlattice effects. These results constrain theoretical models and open the perspective that Γ-valley flat bands might be involved in the correlated physics of twisted WSe2.

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