Detecting Symmetry Breaking in Magic Angle Graphene Using Scanning Tunneling Microscopy.

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Materials

Background:

• Magic angle twisted bilayer graphene exhibits spontaneous symmetry-breaking transitions.
• The relationship between symmetry breaking and superconductivity is of significant interest.
• Experimental identification of symmetry-breaking orders has been challenging.

Purpose of the Study:

• To demonstrate atomically resolved scanning tunneling microscopy (STM) as a tool for identifying symmetry-breaking order.
• To analyze sublattice polarization and Kekulé distortions for order parameter identification.
• To investigate the Kramers intervalley coherent state and its magnetic field response.

Main Methods:

• Atomically resolved scanning tunneling microscopy (STM).
• Analysis of sublattice polarization patterns.
• Characterization of Kekulé distortions in applied magnetic fields.

Main Results:

• STM can serve as a fingerprint for symmetry-breaking order in twisted bilayer graphene.
• Order parameters for competing symmetry-breaking states are identifiable.
• The Kramers intervalley coherent state exhibits a magnetic-field-dependent Kekulé distortion.

Conclusions:

• Atomically resolved STM is a powerful probe for understanding symmetry breaking in magic angle twisted bilayer graphene.
• The study provides a method to distinguish between different symmetry-breaking states.
• Unique magnetic field signatures are identified for specific theoretical ground states.