A local metallic state in globally insulating $La_{1.24}Sr_{1.76}Mn_2O_7$ well above the metal-insulator transition

TL;DR

This study uses angle-resolved photoemission spectroscopy to reveal a local metallic state in $La_{1.24}Sr_{1.76}Mn_2O_7$ that exists well above the global metal-insulator transition, highlighting phase separation effects.

Contribution

It demonstrates the existence of a local metallic phase above the global transition temperature, emphasizing the importance of electronic phase separation and percolation in this manganite.

Findings

Identified local metallic behavior above the global transition temperature.

Showed the system is a metal below $T_C$, a local metal between $T_C$ and $T^*$, and an insulator above $T^*$.

Highlighted the role of phase separation in the metal-insulator transition.

Abstract

Angle-resolved photoemission spectroscopy was used to investigate the evolution of the electronic structure across the metal-insulator transition in bi-layer manganite $La_{1.24}Sr_{1.76}Mn_2O_7$. We found that this system is a metal for $T<T_C$, a local metal but global insulator for $T<T_C<T^*$, and a global insulator for $T>T^*$. These results indicate the critical role of electronic phase separation and percolation effects for the metal-insulator transition in $La_{1.24}Sr_{1.76}Mn_2O_7$.