Thermoelectric power and resistivity of HgBa₂CuO_4+δ over a wide doping range

Thermoelectric power (TEP) and resistivity were systematically investigated for HgBa₂CuO_4+δ (Hg-1201) with various doping levels from high underdoping to slight overdoping. Polycrystalline Hg-1201 samples were carefully prepared from a mixture of HgO, BaO, and CuO. We paid particular attention to carbon impurity in the starting materials, resulting in a high-quality sample. This enabled us to measure reliable transport properties. Assuming one characteristic temperature T* for each doping level, both the TEP and the resistivity can be well scaled, as was reported in the other high- T_c superconductors. The doping dependence of T’s is in good agreement with that of spin gap temperatures determined by NMR as well as that of the pseudogap temperatures reported in some other high- T_c superconductors.