Flat Γ Moiré Bands in Twisted Bilayer WSe_{2}

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Matter

Background:

• Transition metal dichalcogenide moiré systems exhibit correlated phases at various filling levels, offering insights into metal-insulator transitions.
• Understanding the emergence of exotic states of matter near these transitions is crucial for novel electronic applications.

Purpose of the Study:

• To investigate moiré superlattice effects in twisted WSe2 (tWSe2) using combined real- and momentum-space mapping.
• To identify and characterize the electronic band structure, particularly flat bands, and their relation to correlated phenomena.

Main Methods:

• Utilized combined real- and momentum-space mapping techniques for detailed electronic structure analysis.
• Employed advanced data analysis to directly quantify the moiré potential within the tWSe2 system.

Main Results:

• Observed a split-off flat band originating from the monolayer Γ valley states in tWSe2.
• Quantified the moiré potential, revealing its significant influence on the electronic structure.
• Found the global valence band maximum, derived from K valley states, to be energetically close to the Γ-derived flat band but less affected by moiré potentials.

Conclusions:

• The identified Γ-valley flat band is a key feature in twisted WSe2, distinct from K-valley states.
• These findings provide crucial constraints for theoretical models of correlated physics in moiré systems.
• Suggests that Γ-valley flat bands may play a significant role in the observed correlated physics of twisted WSe2.