Quantum critical phase of FeO spans conditions of Earth's lower mantle

Wai-Ga D Ho; Peng Zhang; Kristjan Haule; Jennifer M Jackson; Vladimir Dobrosavljević; Vasilije V Dobrosavljevic

doi:10.1038/s41467-024-47489-w

Quantum critical phase of FeO spans conditions of Earth's lower mantle

Nat Commun. 2024 Apr 24;15(1):3461. doi: 10.1038/s41467-024-47489-w.

Authors

Wai-Ga D Ho^#¹, Peng Zhang^#², Kristjan Haule³, Jennifer M Jackson⁴, Vladimir Dobrosavljević¹, Vasilije V Dobrosavljevic^{5

6}

Affiliations

¹ Department of Physics and National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL, USA.
² MOE Key Laboratory for Non-equilibrium Synthesis and Modulation of Condensed Matter, Shaanxi Province Key Laboratory of Advanced Functional Materials and Mesoscopic Physics, School of Physics, Xi'an Jiaotong University, 710049, Xi'an, Shaanxi, PR China. zpantz@mail.xjtu.edu.cn.
³ Center for Materials Theory, Department of Physics, Rutgers University, Piscataway, NJ, USA.
⁴ Seismological Laboratory, California Institute of Technology, Pasadena, CA, USA.
⁵ Seismological Laboratory, California Institute of Technology, Pasadena, CA, USA. vasilije@carnegiescience.edu.
⁶ Earth and Planets Laboratory, Carnegie Institution for Science, Washington, DC, USA. vasilije@carnegiescience.edu.

^# Contributed equally.

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 t_2g orbital and a band gap in the e_g 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.