Large-bipolaron transport and cuprate superconductors

The in-plane electronic transport of large bipolarons that move within parallel conducting sheets is considered. The Coulomb interactions between the heavy bipolarons in this planar system produce a distinctive spectrum for collective excitations. Transport of the quasiparticles associated with the collective excitations is treated via the conventional Boltzmann transport theory. However, the scattering of the heavy quasiparticles by acoustic phonons is taken to be analogous to the distinctive scattering of individual large polarons. In particular, as with strong-coupling (adiabatic) large polarons, the scattering time is taken to be proportional to the quasiparticle effective mass. The resistivity, the Hall effect, and the thermoelectric power are determined with this scheme. With a constant density of carriers, the resistivity is proportional to the temperature. The Hall number, the number of carriers deduced from the reciprocal of the Hall constant, exceeds the true carrier density by a ratio that rises linearly with temperature. In addition, the thermoelectric power falls in magnitude and ultimately changes sign as the temperature is raised. These unusual transport properties, as well as the ir conductivity, are consistent with the observed behaviors of the high-${\mathit{T}}_{\mathit{c}}$ cuprate superconductors.