Y89NMR evidence for a fermi-liquid behavior inYBa2Cu3O6+x

Abstract

We report NMR shift \ensuremath{\Delta}K and ${T}_{1}$ data of $^{89}\mathrm{Y}$ taken from 77 to 300 K in ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{6+\mathrm{x}}$ for 0.35<x<1, from the insulating to the metallic state. A Korringa law and therefore a Fermi-liqud picture is found to apply for the spin part ${K}_{s}$ of \ensuremath{\Delta}K. The spin contribution ${\ensuremath{\chi}}_{s}$(x,T) to ${\ensuremath{\chi}}_{m}$ is singled out, as the T variation of \ensuremath{\Delta}K scales linearly with the macroscopic susceptibility ${\ensuremath{\chi}}_{m}$. This implies that Cu(3d) and O(2p) holes do not have independent degrees of freedom. Their hybridization, which has a \ensuremath{\sigma} character, hardly varies with doping. These results put severe constraints on theoretical models of high-${T}_{c}$ cuprates.