NMR in ``underdoped'' and ``overdoped'' YBaCuO compounds: fermi-liquid approach

TL;DR

This paper analyzes NMR data of YBaCuO compounds using a Fermi-liquid model, attributing differences in doping levels to a peak in the density of states near the Fermi level caused by a van Hove singularity.

Contribution

It introduces a Fermi-liquid based interpretation of NMR data that accounts for doping-dependent differences via a shift in the chemical potential related to a van Hove singularity.

Findings

The temperature dependence of NMR parameters can be explained by a density of states peak.

Differences between underdoped and overdoped compounds are due to chemical potential shifts.

A van Hove singularity in the spectrum accounts for observed NMR variations.

Abstract

We examine the NMR experimental data for the normal state of YBa$_2$Cu$_3$O$_{7-\delta}$ 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.