Orbital mixing and nesting in the bilayer manganites La$_{2-2x}$Sr$_{1+2x}$Mn$_2$O$_7$

TL;DR

This study uses first-principles calculations to analyze how orbital mixing and Fermi surface nesting in bilayer manganites vary with doping, revealing complex momentum-dependent interactions and their influence on electronic structure.

Contribution

It provides new insights into the doping-dependent orbital interactions and Fermi surface nesting in La$_{2-2x}$Sr$_{1+2x}$Mn$_2$O$_7$ using first-principles methods.

Findings

Strong momentum-dependent interactions between Mn $e_g$ orbitals.

Doping-dependent Fermi surface nesting behavior.

Variation of Jahn-Teller distortion with doping.

Abstract

A first principles study of La$_{2-2x}$Sr$_{1+2x}$Mn$_2$O$_7$ compounds for doping levels $0.3\leq x\leq 0.5$ shows that the low energy electronic structure of the majority spin carriers is determined by strong momentum dependent interactions between the Mn $e_g$ $d_{x^2-y^2}$ and $d_{3z^2-r^2}$ orbitals, which in addition to an $x$ dependent Jahn-Teller distortion, differ in the ferromagnetic and antiferromagnetic phases. The Fermi surface exhibits nesting behavior that is reflected by peaks in the static susceptibility, whose positions as a function of momentum have a non-trivial dependence on $x$.