Experimental evidence for bipolaron condensation as a mechanism for the metal-insulator transition in rare-earth nickelates.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 29311661.
- Also identified by DOI 10.1038/s41467-017-02561-6 and PMC identifier 5758760.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
Many-body effects produce deviations from the predictions of conventional band theory in quantum materials, leading to strongly correlated phases with insulating or bad metallic behavior. One example is the rare-earth nickelates RNiO<sub>3</sub>, which undergo metal-to-insulator transitions (MITs) whose origin is debated. Here, we combine total neutron scattering and broadband dielectric spectroscopy experiments to study and compare carrier dynamics and local crystal structure in LaNiO<sub>3</sub> and NdNiO<sub>3</sub>. We find that the local crystal structure of both materials is distorted in the metallic phase, with slow, thermally activated carrier dynamics at high temperature. We further observe a sharp change in conductivity across the MIT in NdNiO<sub>3</sub>, accompanied by slight differences in the carrier hopping time. These results suggest that changes in carrier concentration drive the MIT through a polaronic mechanism, where the (bi)polaron liquid freezes into the insulating phase across the MIT temperature.