Extraction of the pseudogap energy scale from the static magnetic susceptibility of single and doubleCuO2 planehigh-Tc cuprates

Abstract

The effect of added holes per CuO2 plane, p, on the temperature-dependent uniform(q = 0, whereq is the wavevector)magnetic susceptibility, χ(T), of double CuO2 plane YBa2Cu3O7−δ and single CuO2 plane La2−xSrxCuO4 compounds was investigated over a wide range of oxygen deficiencies(δ) and Sr contents(x). Systematicvariations in χ(T) werefound with changing p. The characteristic pseudogap energy scale,εg(p), was extracted from theanalysis of the χ(T,p) data.From the evolution of εg(p), we have found quite abrupt signs of the pseudogap in the quasi-particlespectral density appearing first at around a planar hole content ofp = 0.190 ± 0.005.εg(p) rapidly grows (almost linearly) with decreasingp. In the heavilyunderdoped region, εg(p) extrapolates to ∼Jex (the antiferromagnetic exchange energy of the parent compound) as . These characteristic features of the pseudogap energy scale are almost identical forYBa2Cu3O7−δ and La2−xSrxCuO4 even though the superconducting transition temperature,Tc, and anisotropy are widely different for these two compounds. We have scrutinizeddifferent existing scenarios for the pseudogap in the light of our findings.