Imaging the flat bands of magic-angle graphene reshaped by interactions

Area of Science:

• Condensed Matter Physics
• Quantum Materials Science

Background:

• Electron interactions are crucial for quantum phases in materials.
• Magic-angle twisted bilayer graphene (MATBG) exhibits intriguing quantum phases due to flat bands.
• High-resolution momentum-space probes are needed to understand MATBG's energy bands.

Purpose of the Study:

• To directly image the interacting energy bands of MATBG with unprecedented resolution.
• To elucidate the nature of flat bands and electron behavior in MATBG.
• To establish the quantum twisting microscope (QTM) as a tool for quantum material spectroscopy.

Main Methods:

• Utilized the quantum twisting microscope (QTM).
• Performed high-resolution imaging of energy bands in momentum space.
• Studied MATBG at and away from the magic angle, including doping effects.

Main Results:

• Observed bands transform significantly at the magic angle due to interactions.
• Identified distinct light and heavy electronic character within the same bands.
• Documented interaction-induced bandwidth renormalization, Mott-like cascades, and Dirac revivals.
• Discovered a persistent low-energy excitation linked to the heavy electron sector.

Conclusions:

• The dual nature of electrons in MATBG arises from different momenta within topological heavy-fermion-like flat bands.
• QTM provides unprecedented insight into electron interactions and quantum phenomena in MATBG.
• This work opens new avenues for high-resolution spectroscopic studies of quantum materials.