Transport in a classical model of a one-dimensional Mott insulator: Influence of conservation laws

We study numerically how conservation laws affect the optical conductivity sigma(omega) of a slightly doped one-dimensional Mott insulator. We investigate a regime where the average distance between charge excitations is large compared to their thermal de Broglie wavelength and a classical description is possible. Due to conservation laws, the dc conductivity is infinite and the Drude weight D is finite even at finite temperatures. Our numerical results test and confirm exact theoretical predictions for D both for integrable and non-integrable models. Small deviations from integrability induce slowly decaying modes and, consequently, low-frequency peaks sigma (omega), which can be described by a memory matrix approach.