Competition of d ‐wave superconductivity and antiferromagnetism in the extended Hubbard model. Superfluid properties

We analyze a competition between d ‐wave superconductivity (SC) and antiferromagnetism (AF) and show the influence of these phenomena on the superfluid stiffness. We deal with the extended Hubbard model on a 2D square lattice with the nn and nnn hopping ( t – t ′– U – W model) in the BCS‐Hartree–Fock approximation. Thermodynamic analysis shows that both, second or first order phase transition between the AF, SC and mixed AF + SC phases are possible. The homogeneous mixed phase or phase separation can be stabilized depending on interaction parameters, band structure and band filling. The corresponding temperature phase diagrams are determined. In the coexistence region we investigate the influence of the antiferromagnetism on the superfluid properties. In the mixed AF + SC ground state the superfluid density is reduced with growing antiferromagnetic ordering and vanishes at half–filling. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)