Interplay between topological valley and quantum Hall edge transport.

Area of Science:

• Condensed Matter Physics
• Materials Science

Background:

• Topologically protected states are typically created using magnetic fields in 2D electron gases, forming quantum Hall edge channels.
• Bilayer graphene exhibits topologically protected states at stacking domain walls, even without magnetic fields.
• The interplay between these two types of topological states is not well understood.

Purpose of the Study:

• Investigate the interplay between topological domain wall states and quantum Hall edge transport.
• Focus on the eight-fold degenerate zeroth Landau level in high-quality suspended bilayer graphene.

Main Methods:

• Utilized high-quality suspended bilayer graphene.
• Applied varying magnetic fields to observe transport phenomena.
• Measured two-terminal conductance across distinct quantum Hall states.

Main Results:

• Two-terminal conductance remained constant at low magnetic fields due to channel trading between domain walls and device edges.
• Observed transport suppression at domain walls at high magnetic fields.
• Evidence suggests the emergence of spectral minigaps at domain walls.

Conclusions:

• Stacking domain walls in bilayer graphene may not represent true topological domain walls in the order parameter.
• The observed transport suppression indicates a deviation from expected topological behavior at higher magnetic fields.