Electronic structure of new superconductor La0.5Th0.5OBiS2: DFT study

Abstract

a b s t r a c tWe studied from first-principles the recently discovered BiS 2 -layered superconductor La 0.5 Th 0.5 OBiS 2 and compared with LaO 0.5 F 0.5 BiS 2 . Firstly, we have performed a global geometry optimization in order to predict an accurate ground state. In contract to the parent semiconductor LaOBiS 2 and according to other recent works, the band structure of both materials presents superconducting behavior, four bands of Bi6p orbitals that cross a Fermi-level. Additionally, the systematic study of the electronic properties as a function of pressure shows the same behavior in both materials "Enhancement of superconductivity T C ", where the Fermi-level is shifted upward and the Fermi surface presents a similar dispersion. These similarities between tetravalent cation electron-doped via Th þ4 substitution for La þ3 (La 0.5 Th 0.5 OBiS 2 ), and monovalent anion electron-doped via F À substitution for O 2À (LaO 0.5 F 0.5 BiS 2 ) may predict the same electronic properties.

Structures and optical absorption of Bi2OS2 and LaOBiS2

“…[13][14][15][16][17] The semiconductivity of LaOBiS2 single crystals has been reported with its forbidden band of 0.86 eV deduced from a Hall measurement above ~300 o C. [8] Nonetheless, a recent report has shown its band gap to be 0.08 eV, which can be attributed to the n-type doping feature in LaOBiS2. [18] Moreover, metallic conductivity has been reported in Bi2OS2 powder; [10] however, it can be understood by the conductivity of the Bi metal, which was detected through XRD.…”

Correlation-Driven Phenomena in Periodic Molecular Systems from Variational Two-electron Reduced Density Matrix Theory

“…Hydrogen chain symmetric dissociation curves were computed with H 10 in the unit cell, using the correlation-consistent polarized valence double-zeta (cc-pVDZ) [59] basis set. Both molecular and periodic calculations were completed in a [10,20] active space. Additional calculations were performed using DFT (B3LYP functional), configuration interaction with single and double excitations (CISD), and Møller-Plesset 2nd-order perturbation theory (MP2) methods.…”

“…Computing the electronic structure of extended molecules and materials can reveal important information such as the band gap, reactivity, and bulk properties like conductivity or polarizability. As such, accurate methods for computing the electronic structure of materials is of interest to many fields, including the study of inorganic polymers, organic electronics, semiconductors, and superconductors [1][2][3][4][5][6][7][8][9][10][11][12]. Electronic structure calculations on extended materials are only computationally tractable in cases where periodic boundary conditions can be imposed, which separate the electrons and orbitals into smaller, periodically repeating, unit cells.…”

Theoretical aspects of the study on the new bismuth chalcogenide based superconductors

“…The band structure of BiCh2 based superconductors has been obtained by first principles band calculations [16,[31][32][33][34][36][37][38][39][40][41]. The band structures of Bi4O4S3 and LaOBiS2 calculated without spin orbit coupling are shown in Fig.…”