Abstract
Transport properties of tetragonal iron monosulfide, mackinawite, show a range of complex features. Semiconductive behavior and proximity to metallic states with nodal superconductivity mark this d-band system as unconventional quantum material. Here, we use the density functional dynamical mean-field theory (DFDMFT) scheme to comprehensively explain why tetragonal FeS shows both semiconducting and metallic responses in contrast to tetragonal FeSe which is a pseudogaped metal above the superconducting transition temperature. Within local-density-approximation plus dynamical mean-field theory (LDA+DMFT) we characterize its paramagnetic insulating and metallic phases, showing the proximity of mackinawite to selective Mott localization. We report the coexistence of pseudogaped and anisotropic Dirac-like electronic dispersion at the border of the Mott transition. These findings announce a new understanding of many-particle physics in quantum materials with coexisting Dirac-fermions and pseudogaped electronic states at low energies. Based on our results we propose that in electron-doped FeS substantial changes would be seen when the metallic regime was tuned towards an electronic state that hosts unconventional superconductivity.
Highlights
Template we show its orbital-selective electronic reconstruction at the border of the first-order Mott-Hubbard metal-insulator transition point
It is important to explore the physical mechanism which generates such a topological anomaly in the non-magnetic electronic structure of layered iron-chalcogendes. With this caveats in mind, in this work we reveal a novel aspect of Dirac fermion physics in iron-chalcogenides which is intrinsically tied with their correlated multi-band nature
Within the tetragonal structure, and using lattice parameters taken from experimental data[41], one-electron band structure calculations based on local-density-approximation (LDA) were performed for the parent compound FeS using the linear muffin-tin orbitals (LMTO) scheme[47,48]
Summary
Template we show its orbital-selective electronic reconstruction at the border of the first-order Mott-Hubbard metal-insulator transition point. Similar to tetragonal FeSe superconductor[33], low-temperature heat transport measurements suggest nodal superconductivity gap in metallic FeS32 This new class of iron-based superconducting materials (which are prepared under hydrothermal reactions28,31) exhibits paramagnetic behavior with different residual resistivity values[27,31,32] and large effective mass anisotropy[31]. The localized nature of hexagonal FeS (troilite) and its correlated electronic structure has been investigated by photoemission (PES) and inverse-photoemission spectroscopy experiments[39] Based on this seminal study it is known that the Fe 3d bandwidth in PES spectra is 25-to-30% narrower than that predicted by first-principles band-structure calculations. A proper microscopic description of localization-delocalization transition[26,45] and the possibility of finding massive Dirac-fermions[11] in 11 iron-chalcogenide systems is important for understanding the role played by dynamical correlations in the low-energy electronic states of iron-based superconductors. In this work we provide new insights to the problem of multi-orbital (MO) electron-electron interactions in tetragonal FeS, revealing the emergence of an orbital-blocked phase[46] with linear spectrum and its possible implications for Kondo-like mass enhancement of Dirac fermions in iron-based superconductors[8]
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