Disordered two-dimensional superconductors: roles of temperature and interaction strength

Abstract

We have considered the half-filled disordered attractive Hubbard model on a square lattice, in which the on-site attraction is switched off on a fraction $f$ of sites, while keeping a finite $U$ on the remaining ones. Through Quantum Monte Carlo (QMC) simulations for several values of $f$ and $U$, and for system sizes ranging from $8\times 8$ to $16\times 16$, we have calculated the configurational averages of the equal-time pair structure factor $P_s$, and, for a more restricted set of variables, the helicity modulus, ${\rho }_s$, as functions of temperature. Two finite-size scaling {\it ansatze} for $P_s$ have been used, one for zero-temperature and the other for finite temperatures. We have found that the system sustains superconductivity in the ground state up to a critical impurity concentration, $f_c$, which increases with $U$, at least up to U=4 (in units of the hopping energy). Also, the normalized zero-temperature gap as a function of $f$ shows a maximum near $f\sim 0.07$, for $2\lesssim U\lesssim 6$. Analyses of the helicity modulus and of the pair structure factor led to the determination of the critical temperature as a function of $f$, for $U=3,$ 4 and 6: they also show maxima near $f\sim 0.07$, with the highest $T_c$ increasing with $U$ in this range. We argue that, overall, the observed behavior results from both the breakdown of CDW-superconductivity degeneracy and the fact that free sites tend to "push" electrons towards attractive sites, the latter effect being more drastic at weak couplings.

9 two-column pages, 14 figures, RevTeX

References in corpus (13)

• Carbon substitution in MgB2 single crystals: structural and superconducting properties
• Critical temperature for the two-dimensional attractive Hubbard Model
• Quantum superconductor-metal transition in a proximity array
• Influence of quenched dilution on the quasi-long-range ordered phase of the 2d XY model
• Effect of inhomogeneity on s-wave superconductivity in the attractive Hubbard model
• Mesoscopic Phase Separation in Anisotropic Superconductors
• Developments in the negative-U modelling of the cuprate HTSC systems
• Correlations in the low-temperature phase of the two-dimensional XY model
• s-wave Superconductivity Phase Diagram in the Inhomogeneous Two-Dimensional Attractive Hubbard Model
• Destruction of Superconductivity by Impurities in the Attractive Hubbard Model
• A layering model for superconductivity in the borocarbides
• Preparation and properties of amorphous MgB${}_2$/MgO superstructures: A new model disordered superconductor
• Critiquing Variational Theories of the Anderson-Hubbard Model: Real-Space Self-Consistent Hartree-Fock Solutions

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