Visualizing interaction-driven restructuring of quantum Hall edge states

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Physics

Background:

• Topological phases feature boundary modes sensitive to electronic interactions.
• Quantum Hall edge states, while studied, have eluded detailed understanding of interaction effects due to experimental challenges.
• Previous methods lacked microscopic resolution and were complicated by edge disorder.

Purpose of the Study:

• To investigate the impact of electronic correlations on quantum Hall edge states in graphene.
• To provide high-resolution, microscopic insights into the internal structure of edge channels.
• To explore interaction-induced modifications in both integer and fractional quantum Hall states.

Main Methods:

• Utilized scanning tunnelling microscopy (STM) for high spatial resolution imaging.
• Studied electrostatically defined quantum Hall edge states in graphene.
• Applied STM to both integer and fractional quantum Hall phases.

Main Results:

• Demonstrated that correlations dictate edge channel structure at magnetic and atomic scales.
• Observed interaction-induced renormalization of edge velocity and spatial profiles for co-propagating modes.
• Discovered unexpected edge valley polarization in integer quantum Hall states, differing from bulk properties.
• Detected spectroscopic signatures of interactions in fractional quantum Hall states (chiral Luttinger liquid).

Conclusions:

• Scanning tunnelling microscopy is a powerful tool for probing edge physics in 2D topological phases.
• Electronic interactions significantly modify quantum Hall edge states, with some effects beyond mean-field theory.
• The study provides a microscopic understanding of edge state behavior and interaction effects in graphene.