Topological Transport Properties in Bilayer Graphene

Bilayer graphene exhibits a remarkable interplay between crystallographic stacking, electronic band topology and external fields. When two graphene layers are arranged in the Bernal (AB) configuration and subjected to a perpendicular electric displacement field, a tunable bandgap emerges. This broken inversion symmetry endows low-energy carriers with non-trivial Berry curvature, giving rise to the valley Hall effect and chiral edge channels at interfaces between regions of opposite gating or stacking order. Introduced twists or strain generate moiré superlattices and domain walls that host one-dimensional topologically protected modes. These channels support low-dissipation transport, robust against backscattering, and offer routes to valleytronics and quantum devices. Control over twist angle, displacement field and stacking domains thus enables the engineering of valley-polarised currents and novel quantum phases in a platform compatible with standard device fabrication techniques.

Research from Nature Portfolio

Recent studies have uncovered key aspects of moiré engineering and edge-state transport. Investigations of bilayer graphene aligned with hexagonal boron nitride at 0° and 60° have revealed non-identical moiré twins, demonstrating that atomic relaxation strongly modulates local Berry curvature and valley Hall response beyond simple periodicity arguments. Work on marginally twisted bilayers at very small angles reported giant Aharonov–Bohm oscillations in a network of chiral one-dimensional channels, with oscillation amplitudes reaching tens of per cent of the resistivity and persisting to elevated temperatures. Seminal imaging experiments have directly visualised topological edge states at AB–BA domain walls by scanning tunnelling microscopy, mapping their spatial distribution and confirming robustness under high magnetic fields. Together, these findings clarify how stacking domains and moiré patterns govern one-dimensional topological transport in bilayer graphene.

Topological Transport Properties in Bilayer Graphene publication trend

The graph below shows the total number of articles in topological transport properties in bilayer graphene across all publications each year (not limited to Nature Index journals).

Technical terms

Berry curvature: A momentum-space quantity capturing the geometrical phase of Bloch electrons, responsible for transverse (Hall) currents in the absence of magnetic fields.

Moiré superlattice: A large-scale periodic pattern arising from slight rotational misalignment or lattice mismatch between stacked two-dimensional layers, modulating local electronic properties.

Domain wall: A one-dimensional interface between regions of differing stacking order or gating polarity, which can host topologically protected conducting channels.

Valley polarisation: The selective population of electronic states in one of the two inequivalent energy minima (valleys) in graphene’s band structure.

Topologically protected states: Electronic modes that are robust against local disorder or backscattering due to underlying symmetry and global band topology.

References

1. Non-identical moiré twins in bilayer graphene. Nature Communications (2023).
2. Giant oscillations in a triangular network of one-dimensional states in marginally twisted graphene. Nature Communications (2019).
3. Direct imaging of topological edge states at a bilayer graphene domain wall. Nature Communications (2016).
4. Topological Edge States at a Tilt Boundary in Gated Multilayer Graphene. Physical Review X (2013).
5. Deciphering the origin of nonlocal resistance in multiterminal graphene on hexagonal-boron-nitride with ab initio quantum transport: Fermi surface edge currents rather than Fermi sea topological valley currents. Journal of Physics Materials (2018).
6. Gate controlled valley polarizer in bilayer graphene. Nature Communications (2020).