Unravelling the intrinsic and robust nature of van Hove singularities in twisted bilayer graphene I. Brihuega (1), P. Mallet (2), H. González-Herrero (1), G. Trambly de Laissardière (3), M. M. Ugeda (1), L. Magaud (2), J.M. Gómez-Rodríguez (1), F. Ynduráin (1), and J.-Y. Veuillen(2,*) (1): Dept. Física de la Materia Condensada, Universidad Autónoma de Madrid, E-28049 Madrid, Spain (2): Institut Néel, CNRS-UJF, BP 166, F-38042 Grenoble, France (3): Laboratoire de Physique Théorique et Modélisation, Université de Cergy-Pontoise- CNRS, F-95302 Cergy-Pontoise, France Abstract: Extensive scanning tunnelling microscopy and spectroscopy experiments complemented by first principles and parameterized tight binding calculations provide a clear answer to the existence, origin and robustness of van Hove singularities (vHs) in twisted graphene layers. Our results are conclusive: vHs due to interlayer coupling are ubiquitously present in a broad range (from 1° to 10°) of rotation angles in our graphene on 6H-SiC(000-1) samples. From the variation of the energy separation of the vHs with rotation angle we are able to recover the Fermi velocity of a graphene monolayer as well as the strength of the interlayer interaction. The robustness of the vHs is assessed both by experiments, which show that they survive in the presence of a third graphene layer, and calculations, which test the role of the periodic modulation and absolute value of the interlayer distance. Finally, we clarify the origin of the related moiré corrugation detected in the STM images. PACS numbers: 61.48.Gh, 68.37.Ef, 73.20.At, 73.22.Pr Soon after the discovery of the unique electronic properties of graphene [1-3], suggestions were made for engineering the band structure of this material. It has been proposed that periodic potentials with wavelengths in the nanometre range could lead to anisotropic renormalization of the velocity of low energy charge carriers [4] or to the generation of new massless Dirac fermions [5]. Experimental works intended for verifying these theoretical predictions were recently reported [6-8], where the periodic perturbation was generated either by a lattice mismatch with the supporting material or by a self-organized array of clusters. An alternative route for modifying graphene’s band structure would be to exploit a rotation between stacked graphene layers [9]. According to calculations, for large angles