Optical conductivity of one-dimensional Mott insulators

We calculate the optical conductivity of one-dimensional Mott insulators at low energies using a field theory description. The square root singularity at the optical gap, characteristic of band insulators, is generally absent and appears only at the Luther-Emery point. We also show that only few par ticle processes contribute significantly to the optical conductivity over a wide range of frequencies and that the bare perturbative regime is recover ed only at very large energies. We discuss possible applications of our res ults to quasi-one-dimensional organic conductors. DOI: 10.1103/PhysRevLett. 86.680.