This is a report on the new 122 ternary transition-metal pnictide of BaMn2Bi2, which is crystallized from bismuth flux. BaMn2Bi2 adopts ThCr2Si2-type structure (I4/mmm) with a=4.4902(3)Å and ...c=14.687(1)Å; it is antiferromagnetic with anisotropic magnetic susceptibility and semiconducting with a band gap of Eg=6meV. Heat capacity result confirms the insulating ground state in BaMn2Bi2 with the electronic residual Sommerfeld coefficient of γ=0. The high temperature magnetization results show that magnetic ordering temperature is TN ∼400K. Hole-doping in BaMn2Bi2 via potassium in Ba1−xKxMn2Bi2 results in metallic behavior for x=0.10(1), 0.32(1) and 0.36(1). With K-doping, more magnetically anisotropic behavior is observed. Although there is a downturn in electrical resistivity and low-field magnetization data below 4K in>30%-doped crystals, there is no sign of zero resistance or diamagnetism.
Local moment antiferromagnet BaMn2Bi2, the first bismuthide with ThCr2Si2 structure, turns metallic upon K-doping. Display omitted
•BaMn2Bi2 and Ba1−xKxMn2Bi2 (0≤x<0.4) measuring up to 1cm in length have been synthesized from Bi flux reactions.•BaMn2Bi2 is the first bismuthide with ThCr2Si2-type structure.•BaMn2Bi2 is a small gap semiconductor but, upon hole-doping, turns metallic with a downturn in resistivity below 4K.•BaMn2Bi2 is a local moment antiferromagnet with TN ∼400K.
•The use of effective local Coulomb interactions that are dynamical, that is, frequency-dependent, is an efficient tool to describe the effect of long-range Coulomb interactions and screening thereof ...in solids.•Dynamical mean field theory calculations with dynamical interactions (“doubly dynamical mean field theory” or “DDMFT”) allows to incorporate the effects due to the coupling to plasmons or particle-hole excitations into the many-body description of the solid.•We discuss the relation of DDMFT to the combined GW+DMFT method and its simplified version “Screened Exchange DMFT”, as well as the cumulant schemes of many-body perturbation theory.•On the example of the simple transition metal SrVO3, we illustrate the mechanism of the appearance of plasmonic satellite structures in the spectral properties, and discuss implications for the low-energy electronic structure.
The use of effective local Coulomb interactions that are dynamical, that is, frequency-dependent, is an efficient tool to describe the effect of long-range Coulomb interactions and screening thereof in solids. The dynamical character of the interaction introduces the coupling to screening degrees of freedom such as plasmons or particle-hole excitations into the many-body description. We summarize recent progress using these concepts, putting emphasis on dynamical mean field theory (DMFT) calculations with dynamical interactions (“doubly dynamical mean field theory”). We discuss the relation to the combined GW+DMFT method and its simplified version “Screened Exchange DMFT”, as well as the cumulant schemes of many-body perturbation theory. On the example of the simple transition metal SrVO3, we illustrate the mechanism of the appearance of plasmonic satellite structures in the spectral properties, and discuss implications for the low-energy electronic structure.
This collection of articles focuses on different aspects of the study of organic conductors. Recent progress in both theoretical and experimental studies is covered in this Special Issue. Papers on a ...wide variety of studies are categorized into representative topics of chemistry and physics. Besides classical studies on the crystalline organic conductors, applied studies on semiconducting thin films and a number of new topics shared with inorganic materials are also discussed.
A brief introduction into the LDA+DMFT approach for the investigation of correlated electron materials is presented. In this scheme ab initio techniques for the calculation of band structures, such ...as the local density approximation (LDA) or the generalized gradient approximation (GGA), are supplemented by electronic correlations and solved within dynamical mean-field theory (DMFT). In particular, we address a fundamental question: How does the Coulomb repulsion between electrons influence the lattice stability of solids? Results are presented for elemental Fe above the Curie temperature and the iron chalcogenide FeSe. They show that the structural properties of materials such as transition metals and their compounds can only be explained if correlations between the electrons are explicitly taken into account.
In high-transition-temperature (Tc) superconductivity, charge doping is a natural tuning parameter that takes copper oxides from the antiferromagnet to the superconducting region. In the metallic ...state above Tc, the standard Landau's Fermi-liquid theory of metals as typified by the temperature squared (T²) dependence of resistivity appears to break down. Whether the origin of the non-Fermi-liquid behavior is related to physics specific to the cuprates is a fundamental question still under debate. We uncover a transformation from the non-Fermi-liquid state to a standard Fermi-liquid state driven not by doping but by magnetic field in the overdoped high-Tc superconductor Tl₂Ba₂CuO₆₊x. From the c-axis resistivity measured up to 45 T, we show that the Fermi-liquid features appear above a sufficiently high field that decreases linearly with temperature and lands at a quantum critical point near the superconductivity's upper critical field--with the Fermi-liquid coefficient of the T² dependence showing a power-law diverging behavior on the approach to the critical point. This field-induced quantum criticality bears a striking resemblance to that in quasi-two-dimensional heavy-Fermion superconductors, suggesting a common underlying spin-related physics in these superconductors with strong electron correlations.
We review a recent proposal of a first principles approach to the electronic structure of materials with strong electronic correlations. The scheme combines the GW method with dynamical mean field ...theory, which enables one to treat strong interaction effects. It allows for a parameter-free description of Coulomb interactions and screening, and thus avoids the conceptual problems inherent to conventional “LDA+DMFT”, such as Hubbard interaction parameters and double counting terms. We describe the application of a simplified version of the approach to the electronic structure of nickel yielding encouraging results. Finally, open questions and further perspectives for the development of the scheme are discussed.
Transition metal oxides offer a wide spectrum of properties which provide the foundation for a broad range of potential applications. Many of these properties originate from intrinsic coupling ...between lattice deformation and nanoscale electronic and magnetic ordering. Lattice strain thus has a profound influence on the electrical, optical, and magnetic properties of these materials. Recent advances in materials processing have led to the synthesis of low-dimensional single-crystal transition metal oxides, namely, epitaxial ultra-thin films and free-standing nano/microwires. Unlike bulk materials, these systems allow external tuning of uniform strain in these materials to tailor their properties and functionalities.
This paper provides a comprehensive review of recent developments in studies of strain effects in transition metal oxide ultra-thin films and nano/microwires. In epitaxial thin films, biaxial strain is developed as a result of lattice mismatch between the film and the substrate. By choosing different substrates, a wide range of strain can be established at discrete values that allows for exploration of new phase space, enhancement of order parameters, creation of complicated domain textures, and stabilization of new phases. On the other hand, continuous tuning of uniaxial strain is possible in nano/microwires, where a variety of phase transitions and their dynamics could be probed at the single or few-domain scale. We focus on the work of strain-controlled electromechanical response in piezoelectric oxides and strain-induced metal–insulator transitions as well as domain physics in strongly correlated electron oxides. Related nanoscale device applications such as strain sensing and power generation will be highlighted as well.
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