Non-centrosymmetric superconductor Th$$_4$$Be$$_{{33}}$$Pt$$_{{16}}$$ and heavy-fermion U$$_4$$Be$$_{{33}}$$Pt$$_{{16}}$$ cage compounds

Unconventional superconductivity in non-centrosymmetric superconductors has attracted a considerable amount of attention. While several lanthanide-based materials have been reported previously, the number of actinide-based systems remains small. In this work, we present the discovery of a novel cubic complex non-centrosymmetric superconductor $${\text {Th}}_4{\text {Be}}_{{33}}{\text {Pt}}_{{16}}$$ Th 4 Be 33 Pt 16 ($$I{\bar{4}}3d$$ I 4 ¯ 3 d space group). This intermetallic cage compound displays superconductivity below $$T_{\text {c}} = 0.90 \pm 0.04$$ T c = 0.90 ± 0.04 K, as evidenced by specific heat and resistivity data. $${\text {Th}}_4{\text {Be}}_{{33}}{\text {Pt}}_{{16}}$$ Th 4 Be 33 Pt 16 is a type-II superconductor, which has an upper critical field $${\text {H}}_{{\text {c}}2} = 0.27$$ H c 2 = 0.27 T and a moderate Sommerfeld coefficient $$\gamma _{\text {n}} = 16.3 \pm 0.8$$ γ n = 16.3 ± 0.8 mJ $${\text {mol}}^{-1}_{\text {Th}}$$ mol Th - 1 $${\text {K}}^{-2}$$ K - 2 . A non-zero density of states at the Fermi level is evident from metallic behavior in the normal state, as well as from electronic band structure calculations. The isostructural $${\text {U}}_4{\text {Be}}_{{33}}{\text {Pt}}_{{16}}$$ U 4 Be 33 Pt 16 compound is a paramagnet with a moderately enhanced electronic mass, as indicated by the electronic specific heat coefficient $$\gamma _{\text {n}} = 200$$ γ n = 200 mJ $${\text {mol}}^{-1}_{\text {U}}$$ mol U - 1 $${\text {K}}^{-2}$$ K - 2 and Kadowaki–Woods ratio $$A/\gamma ^2 = 1.1 \times 10^{-5}$$ A / γ 2 = 1.1 × 10 - 5 $$\upmu $$ μ $$\Omega $$ Ω cm $${\text {K}}^2$$ K 2 $${\text {mol}}_{\text {U}}^2$$ mol U 2 (mJ)$$^{-2}$$ - 2 . Both $${\text {Th}}_4{\text {Be}}_{{33}}{\text {Pt}}_{{16}}$$ Th 4 Be 33 Pt 16 and $${\text {U}}_4{\text {Be}}_{{33}}{\text {Pt}}_{{16}}$$ U 4 Be 33 Pt 16 are crystallographically complex, each hosting 212 atoms per unit cell.

Solar slow magneto-acoustic-gravity waves: an erratum correction and a revisited scenario

ABSTRACT Slow waves are commonly observed on the entire solar atmosphere. Assuming a thin flux tube approximation, the cut-off periods of slow-mode magneto-acoustic-gravity waves that travel from the photosphere to the corona were obtained in Costa et al. In that paper, however, a typo in the specific heat coefficient at constant pressure cp value led to an inconsistency in the cut-off calculation, which is only significant at the transition region. Due to the abrupt temperature change in the region, a change of the mean atomic weight (by a factor of approximately 2) also occurs, but is often overlooked in analytical models for simplicity purposes. In this paper, we revisit the calculation of the cut-off periods of magneto-acoustic-gravity waves in Costa et al. by considering an atmosphere in hydrostatic equilibrium with a temperature profile, with the inclusion of the variation of the mean atomic weight and the correction of the inconsistency aforementioned. In addition, we measure the dominant periods near a particular active region (AR 1243) as observed by the Atmospheric Imaging Assembly (AIA) on-board the Solar Dynamic Observatory (SDO) on 2011 July 3 and compare them to our analytical results. The cut-off periods obtained analytically are consistent with the corresponding periods measured in observations.

The 3-Dimensional Fermi Liquid Description for the Iron-Based Superconductors

The quasiparticles in the normal state of iron-based superconductors have been shown to behave universally as a 3-dimensional Fermi liquid. Because of interactions and the presence of sharp Fermi surfaces, the quasiparticle energy contains, as a function of the momentum $$\varvec{p}$$ p , a term of the form $$( p - p_0)^3 \ln {( |p-p_0|/p_0)} $$ ( p - p 0 ) 3 ln ( | p - p 0 | / p 0 ) , where $$p = | \varvec{p} |$$ p = | p | and $$p_0$$ p 0 is the Fermi momentum. The electronic specific heat coefficient, magnetic susceptibility (Knight shift), electrical resistivity, Hall coefficient and thermoelectric power divided by temperature follow, as functions of temperature T, the logarithmic formula $$a-b T^2 \ln {(T/T^*)}$$ a - b T 2 ln ( T / T ∗ ) , $$a, \, b$$ a , b and $$T^*$$ T ∗ being constant; these formulae have been shown to explain the observed data for all iron-based superconductors. It is shown that the concept of non-Fermi liquids or anomalous metals which appears in the literature is not needed for descriptions of the present systems. When the superconducting transition temperature $$T_{\mathrm {C}}$$ T C and the b / a value for the resistivity are plotted as functions of the doping content x, there appear various characteristic diagrams in which regions of positive correlation and those of negative correlation between $$T_{\mathrm {C}}$$ T C and b / a are interconnected; from these diagrams, we may make speculations about the types of superconductivity and the crossover between them.

Ab-initio studies of thermal and superconducting properties of HfX2 alloys (X = Tc, Re, and Os)

A systematic study of thermal properties such as the Debye temperature, specific heat coefficient, Grüneisen constant, electron-phonon coupling constant and transition temperature have been carried out using the results of electronic band structure and related characteristics, for hafnium superconducting alloys, namely, HfTc2, HfRe2 and HfOs2. Computation of the electronic band structure and associated properties has been carried out using the tight-binding-linear-muffin-tin-orbital (TBLMTO) method within atomic sphere approximation (ASA). The calculated values have been compared with the available results of literature data.

The Structural, Electronic and Magnetic Properties of ARu2Sb2 (A=Sr, Ba)

The structural, electronic and magnetic properties of ThCr2Si2-type compounds ARu2Sb2 (A=Sr, Ba) with space group I4/mmm (139) were studied by means of Full Potential – Linearized Augmented Plane Wave Method (FP-LAPW) method by using WIEN2K code. The necessary input parameters to perform the ab-initio calculation for ARu2Sb2 (A=Sr, Ba) are taken from ARu2As2 (A=Sr, Ba). To our knowledge the properties of these compounds have not been investigated before. From this work the optimized structural parameters, bulk modulus, electronic specific heat coefficient, Fermi energy, Magnetic moment are obtained and for ARu2Sb2 (A=Sr, Ba). Density of States histograms and Electron density plots are also plotted to analyze the bonding nature between the atoms in these compounds.

Assessment of homotopy perturbation method in nonlinear convective-radiative non-Fourier conduction heat transfer equation with variable coefficient

Analytical solutions play a very important role in heat transfer. In this paper, the He's homotopy perturbation method (HPM) has been applied to nonlinear convective-radiative non-Fourier conduction heat transfer equation with variable specific heat coefficient. The concept of the He's homotopy perturbation method are introduced briefly for applying this method for problem solving. The results of HPM as an analytical solution are then compared with those derived from the established numerical solution obtained by the fourth order Runge-Kutta method in order to verify the accuracy of the proposed method. The results reveal that the HPM is very effective and convenient in predicting the solution of such problems, and it is predicted that HPM can find a wide application in new engineering problems.