Electronic transport in highly dopedLa2−xSrxCuO4superconductors

Abstract

The thermoelectric power, Hall coefficient, and resistivity have been measured on two samples of ${\mathrm{La}}_{2-x}{\mathrm{Sr}}_x\mathrm{Cu}{\mathrm{O}}_4$ with a strontium content of $x=0.2\mathrm{}$ and $x=0.25\mathrm{}$. We observe typical metallic behavior with a strong electron-phonon interaction and a low density of carriers. A large positive peak at a temperature of more than twice the respective superconducting transition temperature suggests a strong phonon-drag contribution to the thermopower. At higher temperatures the thermopower changes sign from positive to negative, a trend that increases with increasing Sr content. A positive Hall coefficient combined with a negative diffusion thermopower implies the presence of more than one type of carrier.