We present a parallel algorithm for numerical calculations for electronic lattice models with interactions and disorder. In this scheme, diagonal and off-diagonal disorder are treated exactly per disorder configuration and interaction effects are evaluated using conserving approximations based on self-consistent perturbation theory. We demonstrate this method by calculating second-order corrections to the local pairing amplitude and specific heat for the attractive Hubbard model.

International Journal of Modern Physics BOct 10, 20010 citations

arXiv:1305.3210 · Physics Letters A

Specific heat of a non-local attractive Hubbard model

E.J. Calegari, Cesar Lobo, S. G. Magalhães, Carlos Mauricio Chaves, A. Troper

Published Apr 27, 2013• 1 citation

arXiv HTML PDF

DOI: 10.1016/j.physleta.2013.04.041

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We study the effect of

U=0

impurities on the superconducting and thermodynamic properties of the attractive Hubbard model on a square lattice. Removal of the interaction on a critical fraction of ${f}_{\mathrm{crit}}\ensuremath{\approx}0.30$ of the sites results in the destruction of off-diagonal long-range order in the ground state. This critical fraction is roughly independent of filling in the range $0.75<\ensuremath{\rho}<1.00$, although our data suggest that

{f}_{\mathrm{crit}}

might be somewhat larger below half filling than at $\ensuremath{\rho}=1$. We also find that the two peak structure in the specific heat is present at

f

both below and above the value which destroys long-range pairing order. It is expected that the high-

T

peak associated with local pair formation should be robust, but apparently local pairing fluctuations are sufficient to generate a low-temperature peak.

{\mathit{T}}_{\mathit{c}}

. These features are also mirrored in the shape of the specific-heat peak around

{\mathit{T}}_{\mathit{c}}

, the separation of the temperature regimes where pair formation and their condensation occur, and in the transfer of spectral weight from the single-particle excitation branch to a pair band in the normal state. \textcopyright{} 1996 The American Physical Society.