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Abstract: It is well known that lattice deformations in graphene couple to the Dirac electrons as effective scalar and gauge fields. In this talk, we carefully revisit this theory and show that the optical component of the atomic displacement field, i.e. the relative motion of the two sublattices, contributes to the pseudogauge field at the same order as the acoustic part. Moreover, we find that the optical contributions effectively screen the pseudogauge field as they always tend to partially restore the rotation symmetry about a carbon atom. Previous studies based on continuum elasticity, which ignores this effect, have therefore systematically overestimated the strength of the pseudomagnetic field.
We illustrate this effect in twisted bilayer graphene and corrugated monolayer graphene using molecular dynamics simulations. In twisted bilayer graphene, optical contributions reduce the pseudomagnetic field induced by the atomic reconstruction of the moiré by almost one order of magnitude. And for corrugated graphene, the minibands near charge neutrality are significantly modified. Only by including the optical component can we match tight-binding to continuum theory calculations.