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It is demonstrated now both experimentally and theoretically that graphene is usually not flat but covered by ripples resulting from both intrinsic flexural instability of two-dimensional membranes and roughness of substrate. Thus charge carriers are not just Dirac fermions but Dirac fermions moving in a curved space. The effect of the corrugations on the electron spectrum can be described in terms of gauge (pseudo-magnetic) fields which result, in particular, in formation of pseudo-Landau levels predicted theoretically and found experimentally . These gauge fields can be used for "strain engineering", including tunable gap opening, quantum pumping [and creation of valley-polarized current. Ripples can induce puddles, that is, charge inhomogeneities. The scattering by the ripples is also one of the limiting factors restricting the charge carrier mobility in graphene.

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Mikhail Katsnelson, University of Nijmegen
Seminar Room 0.03, ETP
Contact: George Marinescu