Symmetric Tensor Coupling in Holographic Mean-Field Theory: Deformed Dirac Cones

Abstract

We extend the holographic mean-field theory to rank-two symmetric tensor order parameter field coupled with fermion. We classify the roles of symmetric tensor order according to the effect on the spectral density: cone-angle change, squashing, and tilting of the spectral light cones. The over-tilted light cone is also achieved in a generalized prescription, which consistently preserves the causality condition. Our results provide agreements between the holographic spectra with those observed in real materials, such as type-II Dirac cones and strained graphene.