Phase coexistence and evolution of insulator-metal transition inNd1-xLaxNiO3(0⩽x⩽1) in presence of correlation and disorder.

In this paper, we revisit the transition from an insulator to a metal in the nickelate systemNd1-xLaxNiO3for 0 ⩽  ⩽ 1. UnsubstitutedNdNiO3( = 0) shows a temperature driven transition from metal to insulator on cooling belowTMI≈200Kaccompanied by a change in crystallographic symmetry from a high-temperature orthorhombic phase to a low-temperature monoclinic phase.LaNiO3( = 1) with a crystallographic phase with Rhombohedral symmetry retains its metallic state until the lowest temperature. We show thatNd1-xLaxNiO3is a prototypical system with correlation and disorder where at one extreme (for 0 <  < 0.3) the substitution by La leads to suppression of the first-order MI transition, which upon further substitution leads to a regime of phase coexistence. Further substitution by La leads to a regime of quantum transport, manifested through weak localization and electron-electron interactions for ⩽ 15 K. We observed that there are two coexisting crystallographic phases with different symmetries for 0.3 ⩽  ⩽ 0.6, which has been established through extensive structural, electrical transport, and Raman spectroscopy investigations. We observed that for the critical composition = xc = 0.3 for the MI transition, the low temperature metallic phase is stabilized by a low temperature rhombohedral phase that evolves from the room temperature orthorhombic phase on cooling. In the mixed phase range at higher temperature ⩾ 50 K, we observed that the resistivity shows a regime of non-Fermi liquid behavior with an approach to saturation resistivity at high temperature asT→∞.