paper

Low-energy optical sum-rule in moiré graphene

arXiv:2312.03819 · doi:10.1103/PhysRevLett.133.196501

Abstract

Few layers of graphene at small twist-angles have emerged as a fascinating platform for studying the problem of strong interactions in regimes with a nearly quenched single-particle kinetic energy and non-trivial band topology. Starting from the strong-coupling limit of twisted bilayer graphene with a vanishing single-electron bandwidth and interlayer-tunneling between the same sublattice sites, we present an {\it exact} analytical theory of the Coulomb interaction-induced low-energy optical spectral weight at all {\it integer} fillings. In this limit, while the interaction-induced single-particle dispersion is finite, the optical spectral weight vanishes identically at integer fillings. We study corrections to the optical spectral weight by systematically including the effects of experimentally relevant strain-induced renormalization of the single-electron bandwidth and interlayer tunnelings between the same sublattice sites. Given the relationship between the optical spectral weight and the diamagnetic response that controls superconducting , our results highlight the relative importance of specific parent insulating phases in enhancing the tendency towards superconductivity when doped away from integer fillings.

arXiv commentMain text: 9 pages, 2 figures, Supplementary information: 10 pages; (v2): Slightly modified title; Includes additional results

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