Conductivity noise study of the insulator-metal transition and phase co-existence in epitaxial samarium nickelate thin films

TL;DR

This study investigates the insulator-metal transition in SmNiO3 thin films through resistivity noise analysis, revealing significant inhomogeneity and phase coexistence driven by lattice-orbital interactions.

Contribution

It introduces a novel noise-based approach to understanding phase coexistence and inhomogeneity in rare-earth nickelates during the insulator-metal transition.

Findings

Normalized noise magnitude is extremely high, indicating percolative conduction.

Non-Gaussian noise components suggest phase coexistence.

Lattice-orbital coupling influences electron transport mechanisms.

Abstract

Interaction between the lattice and the orbital degrees of freedom not only makes rare-earth nickelates unusually "bad metal", but also introduces a temperature driven insulator-metal phase transition. Here we investigate this insulator-metal phase transition in thin films of $\mathrm{SmNiO_3}$ using the slow time dependent fluctuations (noise) in resistivity. The normalized magnitude of noise is found to be extremely large, being nearly eight orders of magnitude higher than thin films of common disordered metallic systems, and indicates electrical conduction via classical percolation in a spatially inhomogeneous medium. The higher order statistics of the fluctuations indicate a strong non-Gaussian component of noise close to the transition, attributing the inhomogeneity to co-existence of the metallic and insulating phases. Our experiment offers a new insight on the impact of lattice-orbital coupling on the microscopic mechanism of electron transport in the rare-earth nickelates.