Long-range nontopological edge currents in charge-neutral graphene

Area of Science:

• Condensed Matter Physics
• Materials Science
• Nanotechnology

Background:

• Van der Waals heterostructures exhibit unique electronic properties, with nonlocal transport phenomena being a key area of research.
• Nonlocal measurements are crucial for uncovering novel transport mechanisms like spin, valley, and topological currents in various 2D materials.
• The origin of giant nonlocality, particularly in graphene at charge neutrality, remains a subject of intense scientific debate.

Purpose of the Study:

• To investigate the underlying cause of giant nonlocality observed in graphene.
• To elucidate the role of edge charge accumulation in nonlocal transport phenomena.
• To understand the influence of magnetic fields and edge disorder on electronic transport in graphene.

Main Methods:

• Utilized a superconducting quantum interference device on a tip (SQUID-on-tip) for nanoscale thermal and scanning gate imaging.
• Performed nonlocal transport measurements on graphene samples.
• Analyzed the impact of magnetic fields and edge disorder on current flow.

Main Results:

• Demonstrated that charge accumulation at graphene edges creates narrow conductive channels responsible for giant nonlocality.
• Observed field-induced decoupling between edge and bulk transport at moderate magnetic fields.
• Revealed exotic charge flow patterns sensitive to edge disorder, where charges can move against the electric field.

Conclusions:

• One-dimensional edge transport, a generic and nontopological phenomenon, explains giant nonlocality in graphene.
• This edge-guided transport is expected in many electronic systems, offering insights into controversial transport mechanisms.
• The findings link nonlocal transport phenomena to long-range electronic states localized at system edges.