NMR in ``underdoped'' and ``overdoped'' YBaCuO compounds: fermi-liquid approach
Abstract
We examine the NMR experimental data for the normal state of YBa
2
Cu
3
O
7−δ
within the Fermi-liquid approach. We show that the observed temperature dependence of the Knight shift and
17
O (
89
Y) relaxation rate in ``underdoped'' (
T
c
=60
K ) compound can be interpreted as resulting from a peak in the density of states near the Fermi level. The possible origin of such peak is the quasi-one-dimensional van Hove singularity in the fermionic spectrum, conjectured by Abrikosov, Gofron and Campuzano. The proposed spectrum allows us to account for the qualitatively different NMR data for ``underdoped'' and ``overdoped''(
T
c
=90
K ) compounds by varying the value of chemical potential only.