Synopsis: Graphene with a twist

A small rotation between layers in multilayer graphene radically alters its electronic properties.
Synopsis figure
Credit: A. Luican et al., Phys. Rev. Lett. (2011)

Stacks of graphene are expected to possess drastically different electronic properties compared to their single-layer components, as a result of interlayer coupling. Theory dictates that graphene’s massless low-energy excitations should disappear, even for the simple bilayer structure. However, experiments have shown that, paradoxically, the electronic properties of single layers somehow survive in layered structures. Theorists have suggested that a relative rotation of one layer with respect to the one below it—a “twist” in the stacking—might be the resolution of the paradox.

Now, in a paper appearing in Physical Review Letters, Adina Luican and collaborators from Rutgers University and the Massachusetts Institute of Technology, both in the US, and the University of Manchester, UK, provide experimental proof of the influence of twisting on the band structure of bilayer graphene. Using scanning tunneling microscopy and spectroscopy, the researchers find that for twist angles above 20°, the electronic properties of the twisted layers are practically indistinguishable from those of single-layer graphene. Based on their measurements, Luican et al. conclude that at small angles, the massless Dirac fermion picture of graphene breaks down and the electronic spectrum is dominated by a saddle point feature, while at large rotation angles, the intersection point in the spectrum shifts to irrelevant high energies and the familiar Dirac energy dispersion is recovered. – Alexios Klironomos


More Features »


More Announcements »

Subject Areas


Previous Synopsis

Soft Matter

Gels settle down

Read More »

Next Synopsis

Semiconductor Physics

Bulk carriers cannot take the strain

Read More »

Related Articles

Focus: Graphene Sliding on Graphene

Focus: Graphene Sliding on Graphene

Creating a bulge in a graphene sheet offers the first measurement of the shear forces between graphene layers, an essential factor in many graphene-based devices. Read More »

Synopsis: Crumpled Graphene

Synopsis: Crumpled Graphene

The crumpling of graphene sheets explains a “soft spot” in the material’s mechanical response. Read More »

Synopsis: Protons in the Fast Lane
Energy Research

Synopsis: Protons in the Fast Lane

A proposed graphene-based material could offer speedy transport of protons without the need for water. Read More »

More Articles