Microscopic description of insulator-metal transition in high-pressure oxygen

Abstract

Unusual metallic states involving breakdown of the standard Fermi-liquid picture of long-lived quasiparticles in well-defined band states emerge at low temperatures near correlation-driven Mott transitions. Prominent examples are ill-understood metallic states in d- and f-band compounds near Mott-like transitions. Finding of superconductivity in solid O2 on the border of an insulator-metal transition at high pressures close to 96 GPa is thus truly remarkable. Neither the insulator-metal transition nor superconductivity are understood satisfactorily. Here, we undertake a first step in this direction by focussing on the pressure-driven insulator-metal transition using a combination of first-principles density-functional and many-body calculations. We report a striking result: the finding of an orbital-selective Mott transition in a pure p-band elemental system. We apply our theory to understand extant structural and transport data across the transition, and make a specific two-fluid prediction that is open to future test. Based thereupon, we propose a novel scenario where soft multiband modes built from microscopically coexisting itinerant and localized electronic states are natural candidates for the pairing glue in pressurized O2.

Microscopic description of localization-delocalization transitions in BaFe2S3

“…6 for n t ≈ 6.0. As a byproduct of this analysis and similar to our earlier LDA+DMFT study on insulator-metal transition in high-pressure oxygen, 30 we propose that changes in n a,σ would induce anisotropic small variations in lattice parameters upon doping the parent compound. Though not probed yet, we predict that the lattice parameters along the ladder plane will increase, while the perpendicular one is expected to remain almost constant as in Fig.…”

Orbital-selective nature of the 3d electronic structure of the ThFeAsN superconductor

“…In the superconducting phase, the one-particle Green's function have normal and anomalous components, yielding renormalized G a,σ propagators which are solved by extending the normal state LDA + DMFT solution to include an explicit pair potential term [40]. Including the s-wave pair-field , the LDA + DMFT propagators for the a = xz, yz orbitals are written as [41]…”

Pressure-induced orbital-selective metal from the Mott insulator BaFe2Se3

“…In addition to band broadening also relevant for the Mott transition is the rearrangement of the 3d electronic structure due to changes in the crystal field splitting under pressure [38]. This nontrivial structural phenomenon acts like an orbital field [39] which modifies the on-site orbital energies [10] or the center of gravity δ a of the LDA 3d manifold a = x 2 − y 2 , 3z 2 − r 2 , xz, yz, xy. As shown in the inset of Fig.…”