Electronic band structure of the superconductorSr2RuO4

Abstract

A local-density electronic-band-structure calculation was performed for a recently discovered non-copper-layered perovskite superconductor, ${\mathrm{Sr}}_{2}$${\mathrm{RuO}}_{4}$. It was found that the electronic structure near the Fermi energy is essentially described by antibonding bands of the Ru d\ensuremath{\varepsilon} and O p\ensuremath{\pi} states. Although two holes in the bands are predominantly situated in a d\ensuremath{\varepsilon}(xy)-p\ensuremath{\pi} state in the ab plane, the hole occupations in the other d\ensuremath{\varepsilon}-p\ensuremath{\pi} states vertical to the plane are not negligibly small, possibly in conjunction with the smallness of tetragonal distortion of the ${\mathrm{RuO}}_{6}$ octahedron. Associated with the antibonding d\ensuremath{\varepsilon}-p\ensuremath{\pi} bands, the density of states at the Fermi energy is relatively high (4.36 states/eVcell) but not enough to account for the observed specific-heat constant ${\ensuremath{\gamma}}_{\mathrm{exp}}$ and temperature-independent magnetic susceptibility ${\mathrm{\ensuremath{\chi}}}_{\mathrm{exp}}$. We found a large Stoner factor, which may explain most of the mass enhancement involved in ${\mathrm{\ensuremath{\chi}}}_{\mathrm{exp}}$. Certain similarities and dissimilarities in the electronic properties to the cuprate superconductors are discussed.