Quantum critical phase of FeO spans conditions of Earth's lower mantle
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1.
California Institute of Technology
Abstract
Seismic and mineralogical studies have suggested regions at Earth’s core-mantle boundary may be highly enriched in FeO, reported to exhibit metallic behavior at extreme pressure-temperature (P–T) conditions. However, underlying electronic processes in FeO remain poorly understood. Here we explore the electronic structure of B1-FeO at extreme conditions with large-scale theoretical modeling using state-of-the-art embedded dynamical mean field theory (eDMFT). Fine sampling of the phase diagram reveals that, instead of sharp metallization, compression of FeO at high temperatures induces a gradual orbitally selective insulator-metal transition. Specifically, at P–T conditions of the lower mantle, FeO exists in an intermediate quantum critical state, characteristic of strongly correlated electronic matter. Transport in this regime, distinct from insulating or metallic behavior, is marked by incoherent diffusion of electrons in the conducting t2g orbital and a band gap in the eg orbital, resulting in moderate electrical conductivity (~105 S/m) with modest P–T dependence as observed in experiments. Enrichment of solid FeO can thus provide a unifying explanation for independent observations of low seismic velocities and elevated electrical conductivities in heterogeneities at Earth’s mantle base.
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Acknowledgement
Work in Florida (W.D.H. and V.D.) was supported by the NSF Grant No. DMR-1822258, and the National High Magnetic Field Laboratory through the NSF Cooperative Agreement No. DMR-1644779 and the State of Florida. Work at Rutgers (K.H.) was supported by the NSF grant No. DMR-2233892. P.Z. acknowledges the support of NSFC grant No.11604255. J.M.J. and V.V.D. are grateful to the National Science Foundation’s Collaborative Study of Earth’s Deep Interior (EAR-2009935) and Geophysics (EAR-1727020) programs for support of this work. A portion of this work benefitted from the MINUTI open-source software, https://www.nrixs.com.
Contributions
These authors contributed equally: Wai-Ga D. Ho, Peng Zhang.
V.D. designed the project. V.V.D. and J.M.J. provided the geophysical context and implications. W.D.H. and P.Z. equally contributed to the computational work and data analysis. K.H. provided the eDMFT code and technical guidance. W.D.H. and V.V.D. produced the figures. V.V.D. and V.D. wrote the original manuscript. All authors discussed the results and commented on the manuscript.
Data Availability
The theoretical data presented in the figures can be found in the Source Data files, which are provided with this paper and in a Zenodo data repository (https://doi.org/10.5281/zenodo.10307816). The full set of theoretical data generated during this study are available from the corresponding author upon reasonable request. Source data are provided with this paper.
Code Availability
The eDMFT code we utilized in this paper was developed by Kristjan Haule, and it is publicly available from Kristjan Haule’s website (http://hauleweb.rutgers.edu/tutorials/index.html). This site also has the appropriate tutorials associated with this code.
Conflict of Interest
The authors declare no competing interests.
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Additional details
- PMCID
- PMC11043421
- National Science Foundation
- DMR-1822258
- National Science Foundation
- DMR-1644779
- National Science Foundation
- DMR-2233892
- National Natural Science Foundation of China
- 11604255
- National Science Foundation
- EAR-2009935
- National Science Foundation
- EAR-1727020
- Caltech groups
- Division of Geological and Planetary Sciences, Seismological Laboratory