Orbital-selective pressure-driven metal to insulator transition in FeO from dynamical mean-field theory

Abstract

In this Letter we report the first LDA+DMFT (method combining Local Density Approximation with Dynamical Mean-Field Theory) results of magnetic and spectral properties calculation for paramagnetic phases of FeO at ambient and high pressures (HP). At ambient pressure (AP) calculation gave FeO as a Mott insulator with Fe 3d-shell in high-spin state. Calculated spectral functions are in a good agreement with experimental PES and IPES data. Experimentally observed metal-insulator transition at high pressure is successfully reproduced in calculations. In contrast to MnO and Fe2O3 (d 5 configuration) where metal-insulator transition is accompanied by high-spin to low-spin transition, in FeO (d 6 configuration) average value of magnetic moment < µ 2 z > is nearly the same in the insulating phase at AP and metallic phase at HP in agreement with X-Ray spectroscopy data (Phys. Rev. Lett. 83, 4101 (1999)). The metal-insulator transition is orbital selective with only t2g orbitals demonstrating spectral function typical for strongly correlated metal (well pronounced Hubbard bands and narrow quasiparticle peak) while eg states remain insulating.

Magnetic collapse and the behavior of transition metal oxides at high pressure

“…To solve the realistic many-body problem, we employ the continuous-time hybridization-expansion quantum Monte Carlo algorithm [34]. The calculations are performed for a cubic rocksalt (B1) crystal structure in the paramagnetic state at a temperature T = 1160 K. We use the following values of the average Hubbard U and Hund's exchange J as estimated [8,[22][23][24][25][26][27]35] previously: U = 8.0 eV and J = 0.86 eV for the Mn 3d orbitals, 7.0 and 0.89 eV for Fe, 8.0 and 0.9 eV for Co, and 10.0 and 1.0 eV for Ni, respectively. The Coulomb interaction has been treated in the density-density approximation.…”

“…In practice, however, these calculations employed different approximations, resulting in various scenarios for the IMT. For example, a local moment collapse at the IMT was found to occur in MnO [22]; for FeO, different calculations predicted either a Mott transition in the high-spin state followed by a slow crossover into the low-spin one [24] or the complete absence of magnetic collapse [23]. In addition, most of these theoretical calculations used experimental equations of state, neglecting the effects of coupling between the electrons and lattice at the IMT [23,24,26].…”

“…This obstacle can be overcome by employing, e.g., a state-of-the-art method for calculating the electronic structure of strongly correlated materials [density functional plus dynamical mean-field theory (DFT+DMFT)] [9,10]. It merges ab initio band-structure techniques, such as the local density approximation (LDA) or the generalized gradient approximation (GGA), with dynamical mean-field theory (DMFT) of correlated electrons [9], providing a good quantitative description of the electronic and lattice properties [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28]. In particular, this advanced theory makes it possible to determine the electronic structure and phase stability of paramagnetic correlated materials at finite temperatures, e.g., near a Mott insulator-metal transition [13][14][15][20][21][22][23][24][25][26][27][28].…”

“…In particular, this advanced theory makes it possible to determine the electronic structure and phase stability of paramagnetic correlated materials at finite temperatures, e.g., near a Mott insulator-metal transition [13][14][15][20][21][22][23][24][25][26][27][28]. The DFT+DMFT approach has been used to study the electronic and structural properties of correlated electron materials [11][12][13][14][15][16][17][18][19][20], including transition metal monoxides [22][23][24][25][26][27][28][29]. In practice, however, these calculations employed different approximations, resulting in various scenarios for the IMT.…”

“…It merges ab initio band-structure techniques, such as the local density approximation (LDA) or the generalized gradient approximation (GGA), with dynamical mean-field theory (DMFT) of correlated electrons [9], providing a good quantitative description of the electronic and lattice properties [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28]. In particular, this advanced theory makes it possible to determine the electronic structure and phase stability of paramagnetic correlated materials at finite temperatures, e.g., near a Mott insulator-metal transition [13][14][15][20][21][22][23][24][25][26][27][28]. The DFT+DMFT approach has been used to study the electronic and structural properties of correlated electron materials [11][12][13][14][15][16][17][18][19][20], including transition metal monoxides [22][23][24][25...…”