Unique dxy superconducting state in the cuprate Ba2CuO3.25

Abstract

Recent discovery of superconductivity at a transition temperature of 73K in the doped layered compound Ba2CuO3+x for x∼0.2 has generated a lot of interest. Experiments in this alternately stacked oxygen octahedral and chain layered structure reveal that a compression of the octahedra causes the Cu-dz2 orbital to lie above the Cu-dx2−y2 orbital unlike in the well-known cuprate superconducting materials. Our first-principles calculations and low-energy Hamiltonian studies on the x = 0.25 system reveal that this energy ordering results in formation of dz2-dominated electron pockets. The strong nesting in the Fermi pockets leads to an AFM spin fluctuation mediated dxy-wave superconducting state dominated by pairing among the dz2 orbitals. This is in contrast to the cuprate superconductors (e.g., YBCO) where both electron and hole pockets exist and the superconducting state with B1g symmetry are formed by the dx2−y2 orbital electrons. Unlike the earlier reports we find the interlayer hybridization has an important contribution to the low-energy band structure and formation of the unconventional superconducting state.

Source-reported materials — not catalogue approval

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