Bilayer splitting and c-axis coupling in bilayer manganites showing colossal magnetoresistance

TL;DR

This study uses angle-resolved photoemission spectroscopy to map the electronic band structure of bilayer manganites, revealing bilayer splitting and c-axis coupling effects that influence colossal magnetoresistance.

Contribution

It provides the first complete mapping of the Fermi surface and bilayer splitting in bilayer manganites, highlighting the role of interplane coupling in CMR.

Findings

Bilayer splitting of the in-plane 3d$_{x^2-y^2}$ band observed.

Full mapping of the 3d$_{3z^2-r^2}$ band achieved.

Interplane coherence diminishes near the CMR transition.

Abstract

By performing angle-resolved photoemission spectroscopy of the bilayer colossal magnetoresistive (CMR) manganite, $La_{2-2x}Sr_{1+2x}Mn_{2}O_{7}$, we provide the complete mapping of the Fermi level spectral weight topology. Clear and unambiguous bilayer splitting of the in-plane 3d$_{x^2-y^2}$ band, mapped throughout the Brillouin zone, and the full mapping of the 3d$_{3z^2-r^2}$ band are reported. Peculiar doping and temperature dependencies of these bands imply that as transition from the ferromagnetic metallic phase approaches, either as a function of doping or temperature, coherence along the c-axis between planes within the bilayer is lost, resulting in reduced interplane coupling. These results suggest that interplane coupling plays a large role in the CMR transition.