On the contrasting spin dynamics of $La_{2-x}Sr_xCuO_4$, $Nd_{2-x}Ce_xCuO_4$ and $YBa_2Cu_3O_{6+x}$ near half filling

TL;DR

This paper uses simple calculations to show how the location of electron or hole pockets in the Brillouin zone influences incommensurability and magnetic phase stability in different cuprate materials near half filling.

Contribution

It provides a comparative analysis of spin dynamics in various cuprates based on the pocket locations, highlighting their impact on magnetic ordering and phase separation tendencies.

Findings

Pockets at $( ext{±}rac{ ext{π}}{2}, ext{±}rac{ ext{π}}{2})$ destabilize antiferromagnetism in LaSrCuO.

Pockets at $( ext{π},0)$ preserve commensurate spin order in NdCeCuO.

Results suggest hole pockets at $( ext{π}/2, ext{π}/2)$ for YBCuO.

Abstract

We present simple calculations which show that incommensurability upon doping and the width of the magnetically ordered phase in Mott-Hubbard insulators depend strongly on the location of the hole/electron pockets in the Brillouin zone. For $LaSrCuO$ systems, we found the pockets at $(\pm \pi/2,\pm \pi/2)$, in which case the corrections to the antiferromagnetic spin stiffness grow with doping and destroy the commensurate antiferromagnetic ordering already at a very small doping. On the other hand, in $NdCeCuO$, the hole pockets are located at $(\pi,0)$ and the symmetry related points, in which case the corrections to the stiffness scale linearly with the density of carriers and do not destroy commensurate spin ordering. For $YBCuO$, systems the situation is less certain, but our results favor hole pockets at $(\pi/2,\pi/2)$. We also discuss briefly the tendency towards phase separation.