Effects of Zn substitution on the superconductivity and pseudogap in HgBa₂CuO_4+δ with various doping levels

A series of high-T_c superconductors HgBa₂Cu_1-xZn_xO_4+δ (Hg-1201, x=0 and 0.03) with various doping levels was synthesized, and the effects of Zn substitution on superconductivity and pseudogap were investigated on the basis of dc susceptibility, thermoelectric power, and electrical resistivity data. T_c decreased with Zn substitution over a wide doping range, but most strongly at a heavily underdoped state, without any appreciable change in hole concentration irrespective of doping level. A disappearance of superconductivity or a sharp drop in T_c by Zn substitution is not observed in the vicinity of p = 1/8, which suggests no enhancement of charge/spin stripe order. Analyses of temperature dependence of Seebeck coefficient S and resistivity revealed that there is no clear change with Zn substitution in the characteristic temperature T* associated with the pseudogap, while the transport data are affected below T* by Zn substitution.