Crossover in the nature of the metallic phases in the perovskite-type RNiO_3

TL;DR

This study investigates the electronic structure changes across the metal-insulator transition in Nd$_{1-x}$Sm$_{x}$NiO$_{3}$, revealing a sharp crossover in the nature of metallic phases near $x \,\sim\, 0.4$ through photoemission spectra.

Contribution

It provides experimental evidence of a sharp change in electronic correlations in RNiO$_3$ near $x \sim 0.4$, highlighting a crossover in metallic phase behavior.

Findings

High spectral intensity at Fermi level for $x \le 0.4$ in metallic phase

Pseudogap-like behavior observed for $x > 0.4$ above $T_{MI}$

Sharp change in electronic correlations at $x \sim 0.4$

Abstract

We have measured the photoemission spectra of Nd$_{1-x}$Sm$_{x}$NiO$_{3}$, where the metal-insulator transition and the N\'{e}el ordering occur at the same temperature for $x \lesssim 0.4$ and the metal-insulator transition temperature ($T_{MI}$) is higher than the N\'{e}el temperature for $x \gtrsim 0.4$. For $x \le 0.4$, the spectral intensity at the Fermi level is high in the metallic phase above $T_{MI}$ and gradually decreases with cooling in the insulating phase below $T_{MI}$ while for $x > 0.4$ it shows a pseudogap-like behavior above $T_{MI}$ and further diminishes below $T_{MI}$. The results clearly establish that there is a sharp change in the nature of the electronic correlations in the middle ($x \sim 0.4$) of the metallic phase of the $R$NiO$_3$ system.