Mott interactions driven insulating behaviour in ruthenium based double perovskites: A2SmRuO6 (A = Ba & Sr)

Double perovskites (DP’s) are important for understanding the diverse physical properties arising from strongly correlated interactions. According to experimental observations, the DP’s A ₂ SmRuO ₆ (A = Ba & Sr) are insulators; however, first-principles calculations using GGA approximations show that they are metallic. We observed a band gap ( E _g) opening of 1.3 eV for Ba ₂ SmRuO ₆ (BSRO) and 1.4 eV for Sr ₂ SmRuO ₆ (SSRO) upon the insertion of Hubbard parameter (U) in the theoretical computations for accounting the electron-electron interactions. Further investigations using core-level spectroscopy reveal E _g of 1.05 eV for BSRO and 0.85 eV for SSRO. Furthermore, the calculations for Δ (charge transfer energy), U (coulomb repulsion energy), and W (bandwidth) from the combined spectra show U < Δ and U/W > 1.15, which confirms these compounds be classified as Mott-Hubbard insulators. These results expand our understanding of the strongly correlated compounds around the Fermi level, which might have applications in optoelectronics.