paper

Collective excitations in a large-d model for graphene

arXiv:1312.2854 · doi:10.1103/PhysRevB.89.125428

Abstract

We consider a model of Dirac fermions coupled to flexural phonons to describe a graphene sheet fluctuating in dimension . We derive the self-consistent screening equations for the quantum problem, exact in the limit of large . We first treat the membrane alone, and work out the quantum to classical, and harmonic to anharmonic crossover. For the coupled electron-membrane problem we calculate the dressed two-particle propagators of the elastic and electron interactions and find that it exhibits a collective mode which becomes unstable at some wave-vector for large enough coupling . The saddle point analysis, exact at large , indicates that this instability corresponds to spontaneous and simultaneous appearance of gaussian curvature and electron puddles. The relevance to ripples in graphene is discussed.

23 pages, 30 figures

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