Twisted graphene bilayers

a-b) Illustration of a moiré pattern arising from a rotation angle of 9.6° and the emergence of van Hove singularities as a consequence of the reciprocal space rotation. c) STM images of several MP with different rotation angle. d)Measure of the of van Hove singularities on the real graphene rotated layers.

Twisted graphene bilayers have emerged recently as a promising graphene based material whose properties can be controlled by a single geometrical parameter which is the interlayer rotation angle. Electronic structure calculations indicate that this angle should lead to a reduction of the Fermi velocity (even to zero), induce low energy van Hove singularities and tend to localize the density of states in real space. We demonstrated experimentally that the expected novel properties for twisted layers show up in the electronic structure in a wide range of rotation angles

Physical Review Letters 109, 196802 (2012) Article