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Based on a careful perusal of data, we revisit the longstanding issues of transport anisotropy and incoherence-coherence crossovers in graphite. Using a realistic many-body approach, we unearth surprising but distinctive signatures of band-selective Kondoesque physics in graphite. The intricate interplay between local multiband Coulomb and effectively enhanced residual spin-orbit interactions comprehensively rationalizes these anomalies in terms of a manifestation of a multiband Kondo effect with a small Fermi liquid coherence scale. [ABSTRACT FROM AUTHOR]

Three-dimensional BÍ2Te2Se topological insulator (TI) reveals itinerant-localized duality of correlated electrons. Motivated thereby, we investigate the role of local, multiorbital electron interactions in bulk BÍ2Te2Se. Within local density approximation plus dynamical mean-field theory (LDA + DMFT), we derive a Kondo-Mott electronic transition with an intermediate Dirac-like phase characterized by linear spectral functions. Mott localization and spin-orbit induced weak antilocalization mark the channel-selective insulating phase. Good semiquantitative agreement with spectroscopy and electrical transport can serve as a theoretical basis for postulating that Mottness is a remarkable way to approach maximally bulk-insulating behavior in real Tis. [ABSTRACT FROM AUTHOR]

We report on bulk electronic structure and transport properties of pure and doped Bi2Se3 topological insulators. Using the local-density approximation plus dynamical mean-field theory for the real multiorbital case, we propose a new scenario in which Bi2Se3 is a selective, multiorbital Kondo system. We derive a filling-controlled metal-to-insulator crossover in this p-band material, predicting a continuous transition to a bulk Kondo insulator upon hole doping. By explicitly including the spin-orbit interaction, good semiquantitative agreement with effective mass and spectral and dc transport responses is obtained. This serves as a theoretical basis for postulating that Bi2Se3 is a sizable correlated electron system close to electronic (or topological) transitions. [ABSTRACT FROM AUTHOR]

The newly discovered 122-iron-chalcogenide superconductors show clear signatures of Mott-insulating and strange, incoherent metal normal states. Motivated thereby, we use local-density approximation plus dynamical mean-field theory (LDA + DMFT) to study the electronic structure and transport properties of KxFe2-ySe2. We find that the undoped KFe1.6Se2 system is a new kind of Mott-Kondo insulator (MKI). Electron doping this MKI drives a Mott transition to an orbital-selective non-Fermi-liquid metal. Good agreement with spectral and transport responses supports our view, implying that superconductivity arises from a doped Mott insulator, as in the high-Tc cuprates. [ABSTRACT FROM AUTHOR]

Recent finding of an unusual in-plane resistivity anisotropy in the underdoped 122 family at high temperature (T) suggests an orbital nematic (ON) order, posing a challenge to extant theories. The sign of the anisotropy contradicts expectations from weakly correlated as well as pure spin-only nematic views. Here, we show how such an ON order with accompanying structural distortion arises from residual, intersite, and interorbital two-body interactions in an incoherent "bad metal" close to Mottness. Enhancement of orbital-selective incoherence is shown to be necessary for understanding transport anisotropy. Our results suggest that ON order, with subsequent antiferromagnetic order, might be the primary competitor to superconductivity in Fe arsenides. [ABSTRACT FROM AUTHOR]

The twin issues of the nature of the "normal" state and competing order(s) in the iron arsenides are central to understanding their unconventional, high-Tc superconductivity. We use a combination of transport anisotropy measurements on detwinned Sr(Fe1-xCox)2As2 single crystals and local density approximation plus dynamical mean field theory (LDA + DMFT) calculations to revisit these issues. The peculiar resistivity anisotropy and its evolution with x are naturally interpreted in terms of an underlying orbital-selective Mott transition (OSMT) that gaps out the dxz or dyz states. Further, we use a Landau-Ginzburg approach using LDA + DMFT input to rationalize a wide range of anomalies seen up to optimal doping, providing strong evidence for secondary electronic nematic order. These findings suggest that strong dynamical fluctuations linked to a marginal quantum-critical point associated with this OSMT and a secondary electronic nematic order constitute an intrinsically electronic pairing mechanism for superconductivity in Fe arsenides. [ABSTRACT FROM AUTHOR]

We perform a combined experimental-theoretical study of the Fe-oxychalcogenides (FeOCh) series La2O2Fe2OM2 (M=S, Se), which are among the latest Fe-based materials with the potential to show unconventional high-Tc superconductivity (HTSC). A combination of incoherent Hubbard features in x-ray absorption and resonant inelastic x-ray scattering spectra, as well as resistivity data, reveal that the parent FeOCh are correlation-driven insulators. To uncover microscopics underlying these findings, we perform local density approximation-plus-dynamical mean field theory (LDA+DMFT) calculations that reveal a novel Mott-Kondo insulating state. Based upon good agreement between theory and a range of data, we propose that FeOCh may constitute an ideal testing ground to explore HTSC arising from a strange metal proximate to a novel selective-Mott quantum criticality. [ABSTRACT FROM AUTHOR]