We report a detailed electronic structure calculation for Vanadium (V) using DFT, DFT+U , G0W0, GW0 and DFT+DMFT methods. The calculated values of W , U and J by cRPA method are ∼1.1, ∼3.4 and ∼0.52 eV, respectively. The comparison between calculated spectra (CS) and experimental spectra (ES) suggests that W (U ) is more accurate for DFT+U (DFT+DMFT) method. The CS, obtained by these methods, give fairly good agreement with ES for peaks' positions except GW0. The shallowness of the dips lying ∼ -1.5 eV and ∼1.0 eV in ES are properly explained by DFT+DMFT method only, due to the presence of incoherent t2g states. This work suggests that for the proper explanation of ES, sophisticated many-body theory is needed even for the simple metal.

Both experimental and theoretical studies show non-trivial topological behaviour in native rocksalt phase for SnS and SnSe and categorize these materials in topological crystalline insulators. Here, the detailed electronic structures studies of SnS and SnSe in the rocksalt phase are carried out using many-body GW based theory and density functional theory both for ground states and temperature dependent excited states. The estimated values of fundamental direct bandgaps around L-point using G 0 W 0 (mBJ) are ∼0.27 (∼0.13) eV and ∼0.37 (∼0.17) eV for SnS and SnSe, respectively. The strength of hybridization between Sn 5p and S 3p (Se 4p) orbitals for SnS (SnSe) shows strong k-dependence. The behaviour of W ¯ (ω), which is the averaged value of diagonal matrix elements of fully screened Coulomb interaction, suggests to use full-GW method for exploring the excited states because the correlation effects within these two materials are relatively weak. The temperature dependent electronic structure calculations for SnS and SnSe provide linearly decreasing behaviour of bandgaps with rise in temperatures. The existence of collective excitation of quasiparticles in form of plasmon is predicted for these compounds, where the estimated values of plasmon frequency are ∼9.5 eV and ∼9.3 eV for SnS and SnSe, respectively. The imaginary part of self-energy and mass renormalization factor (Z k (ω)) due to electron–electron interaction (EEI) are also calculated along W–L–Γ direction for both the materials, where the estimated ranges of Z k (ω) are 0.70 to 0.79 and 0.71 to 0.78 for SnS and SnSe, respectively, along this k-direction. The present comparative study reveals that the behaviour of temperature dependent EEI for SnS and SnSe are the almost same and EEI is important for high temperature transport properties.

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Studies connected with the investigations of "non-Fermi liquid" (NFL) systems continue to attract interest in condensed matter physics community. Understanding the anomalous physical properties exhibited by such systems and its related electronic structures is one of the central research topics in this area. In this context, Ce-based and Ce-site diluted (with nonmagnetic ions) compounds provide a fertile playground. Here, we present a detailed study of non-linear DC susceptibility and combined density functional theory plus dynamical mean field theory (DFT+DMFT) on Ce 0.24 La 0.76 Ge. Theoretical investigation of 4f partial density of states, local susceptibility and self-energy demonstrates the presence of NFL behavior which is associated with fluctuating local moments. Non-linear DC susceptibility studies on this compound reveal that the transition from NFL state to the new phase is due to development of the bi-quadratic exchange coupling and it obeys the non-linear susceptibility scaling. Under the application of magnetic fields, local moments interact spatially through conduction electrons resulting in magnetic fluctuations. Our studies point to the fact that the origin of the observed bi-quadratic exchange coupling is due to the spatial magnetic fluctuations.

In the last few decades, the study of topological materials has been carried out on an extensive scale. Half-Heusler alloys are well known for their topological behaviours. In this work, we present a detailed study of topological properties of a ternary half-Heusler alloy, YAuPb, using the tight-binding approach. We have calculated some important topological properties which includes-finding nodes and their chiralities, Berry curvature (Ω) and the surface-states. Five pairs of characteristic nodes with equal and opposite chiralities are obtained. Based on the study of these properties, we categorise the material as non-trivial topological semimetal. Besides the topological behaviours, we present a comparative study of temperature dependent transport properties corresponding to the chemical potential (μ) of the Fermi level and the node points. The temperature range chosen for the study is 50-300 K. The results obtained from the calculations of electrical conductivity per unit relaxation time (σ/τ ) and the electronic part of thermal conductivity per unit relaxation time (κ 0 ) indicates the conducting nature of the material to both the heat and electricity. At the Fermi level, the value of Seebeck coefficient (S) is found to be ∼ −9.07 (−35.95) μV K −1 at 50(300) K. The negative value of S indicates the n-type behaviour of the compound. The calculated value of electronic specific heat (Pauli magnetic susceptibility) corresponding to Fermi level is ∼ 0.03(0.18) × 10 −2 J mol −1 K −1 (∼ 1.21(1.14) × 10 −10 m 3 mol −1 ) at 50(300) K. This work suggests that YAuPb is a promising candidate of non-trivial topological semimetals which can be employed in transmission of heat and electricity, and as n-type material within the temperature range of 50-300 K.