Transport Criticality in Triangular Lattice Hubbard Model

We study electric transport near the Mott metal-insulator transition. Optical conductivity of the half-filled Hubbard model on a triangular lattice is calculated based on a cellular dynamical mean field theory including vertex corrections inside the cluster. Near the Mott critical end point, we find that a Drude peak on the metallic side smoothly connects to an ingap peak on the insulating side. We find that the weight of these peaks exhibits a critical power-law behavior near the Mott critical end point upon controlling Coulomb repulsion U, vertical bar D - D*vertical bar proportional to vertical bar U - U*vertical bar(1/delta) with an unconventional value of the exponent 1/delta. Although the criticality of thermodynamics is described by the Ising universality class, the obtained value of the exponent 1/delta challenges the general belief that conductivity has the same scaling behavior as order parameter or energy density.