Correlation between the Doping Dependences of Superconducting Gap Magnitude<b>2</b><i>Δ_<b>0</b></i>and Pseudogap Temperature<i><i>T</i>^*</i>in High-<i><i>T</i>_{<b><i>c</i></b>}</i>Cuprates

Abstract

We report that in La 2- x Sr x CuO 4 (La214) and Bi 2 Sr 2 CaCu 2 O 8+δ (Bi2212), the resistivity ρ and magnetic susceptibility χ decrease more sharply below T * , corresponding to the onset temperature of a spin gap (pseudogap) at least for Bi2212. In each system, T * scales with the superconducting gap magnitude 2Δ 0 ( T * ∼2Δ 0 /4.3 k B ), which increases as the doping level is lowered. We also report that 2Δ 0 is almost proportional to T max (> T * ), where T max is the temperature exhibiting a broad peak of χ and k B T max has been considered to give the measure of effective exchange energy J eff ; the α factors in 2Δ 0 ∼α k B T max ∼α J eff are nearly one and two for La214 and Bi2212, respectively.