dc transport and optical conductivity in a resonating-valence-bond crystal

The dc transport and dynamical conductivity of a resonating-valence-bond crystal is studied at finite temperatures. The charge carriers, or holons, are assumed to be bosons which scatter inelastically with neutral spin excitations, or spinons, which are assumed to be gapless fermions. The dc resistivity arising from holon-spinon scattering in lowest order is found to vary with temperature as T3/2. The inelastic scattering leads to a strong temperature dependence in the low-frequency conductivity and enhanced absorption in the midinfrared, in qualitative agreement with reflectivity experiments on high-temperature superconducting oxides. However, from our analysis, it appears unlikely that a single inelastic scattering mechanism can explain all the main features observed in these experiments.