Superconducting transition temperature is studied in the strong-coupling region of the Holstein-Hubbard model that includes both electron-phonon and Coulomb interactions.By combining the dynamical mean field theory with the continuous-time quantum Monte Carlo method, transition temperature is derived numerically.Without Coulomb interaction, our calculation reproduces analytic expressions of the transition temperature for weak and strong coupling limits of electron-phonon interaction.When electron-phonon coupling is strong enough, Coulomb repulsion enhances superconductivity, in contrast to the weak coupling case.The enhancement is due to coherent motion of superconducting pairs that reduce the Coulomb repulsive energy of almost localized electrons.Superconducting transition temperature is studied in the strong-coupling region of the Holstein-Hubbard model that includes both electron-phonon and Coulomb interactions.By combining the dynamical mean field theory with the continuous-time quantum Monte Carlo method, transition temperature is derived numerically.Without Coulomb interaction, our calculation reproduces analytic expressions of the transition temperature for weak and strong coupling limits of electron-phonon interaction.When electron-phonon coupling is strong enough, Coulomb repulsion enhances superconductivity, in contrast to the weak coupling case.The enhancement is due to coherent motion of superconducting pairs that reduce the Coulomb repulsive energy of almost localized electrons.

International Conference on Strongly Correlated Electron Systems (SCES)Jun 16, 20142 citations

Superconductivity in a strongly correlated one-band system

T. Domański, Karol Izydor Wysokiński, R. Ramakumar

We study superconductivity in the extended Hubbard model with a strong on-site repulsion U and weak attractive density-density interaction ${\mathit{V}}_{\mathit{ij}}$ . The electron correlation effects, beyond the weak-coupling regime of U, are included approximately by employing Hubbard decoupling approximations. The formulas for superconducting transition temperature ${\mathit{T}}_{\mathit{c}}$ of the present approach are compared to those obtained with the strong-coupling expansion and slave-boson techniques. The methods share some common features. We discuss behavior of ${\mathit{T}}_{\mathit{c}}$ for superconducting phases with s- and d-wave symmetry of the superconducting order parameter. In contrast to the mean-field treatment of U, we find that the strong on-site repulsion does not destroy superconductivity induced by ${\mathit{V}}_{\mathit{ij}}$0 even when U\ensuremath{\gg}|${\mathit{V}}_{\mathit{ij}}$|. \textcopyright{} 1996 The American Physical Society.We study superconductivity in the extended Hubbard model with a strong on-site repulsion U and weak attractive density-density interaction ${\mathit{V}}_{\mathit{ij}}$. The electron correlation effects, beyond the weak-coupling regime of U, are included approximately by employing Hubbard decoupling approximations. The formulas for superconducting transition temperature ${\mathit{T}}_{\mathit{c}}$ of the present approach are compared to those obtained with the strong-coupling expansion and slave-boson techniques. The methods share some common features. We discuss behavior of ${\mathit{T}}_{\mathit{c}}$ for superconducting phases with s- and d-wave symmetry of the superconducting order parameter. In contrast to the mean-field treatment of U, we find that the strong on-site repulsion does not destroy superconductivity induced by ${\mathit{V}}_{\mathit{ij}}$0 even when U\ensuremath{\gg}|${\mathit{V}}_{\mathit{ij}}$|. \textcopyright{} 1996 The American Physical Society.

Physical review. B, Condensed matterAug 1, 19965 citations

Superconductivity in the Repulsive Hubbard Model

D. Baeriswyl

Journal of Superconductivity and Novel MagnetismDec 21, 201015 citations

Superconducting correlations in the one-band Hubbard model with intermediate on-site and weak attractive intersite interactions

K. P. Jain, R. Ramakumar, C. C. Chancey

In this paper, we analyze a simple extended Hubbard model with an intermediate on-site interaction (both repulsive and attractive) and a weak intersite attractive interaction. Following Hubbard decoupling approximations and introducing Hubbard subband operators, we obtain a generalized gap function for singlet s-wave pairing that explicitly depends on the Hubbard subband energies. For the on-site repulsive-interaction case, we find that the superconductivity is not destroyed in the intermediate-interaction regime, contrary to the prediction of a Hartree-Fock mean-field treatment. The essential consequence of the on-site repulsion is the formation of the Hubbard subbands separated by the Mott-Hubbard gap, and it is within these subbands that pairing induced by the intersite interaction occurs. For the attractive on-site interaction case, the on-site pairing amplitude is found to be proportional to the bandwidth, and the gap function has contributions from both on-site and intersite pairing. The relevance of the model to high-temperature superconductivity is discussed.In this paper, we analyze a simple extended Hubbard model with an intermediate on-site interaction (both repulsive and attractive) and a weak intersite attractive interaction. Following Hubbard decoupling approximations and introducing Hubbard subband operators, we obtain a generalized gap function for singlet s-wave pairing that explicitly depends on the Hubbard subband energies. For the on-site repulsive-interaction case, we find that the superconductivity is not destroyed in the intermediate-interaction regime, contrary to the prediction of a Hartree-Fock mean-field treatment. The essential consequence of the on-site repulsion is the formation of the Hubbard subbands separated by the Mott-Hubbard gap, and it is within these subbands that pairing induced by the intersite interaction occurs. For the attractive on-site interaction case, the on-site pairing amplitude is found to be proportional to the bandwidth, and the gap function has contributions from both on-site and intersite pairing. The relevance of the model to high-temperature superconductivity is discussed.

Physical review. B, Condensed matterDec 1, 19909 citations

We study superconductivity in the extended Hubbard model with a strong on-site repulsion U and weak attractive density-density interaction

{\mathit{V}}_{\mathit{ij}}

. The electron correlation effects, beyond the weak-coupling regime of U, are included approximately by employing Hubbard decoupling approximations. The formulas for superconducting transition temperature

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

of the present approach are compared to those obtained with the strong-coupling expansion and slave-boson techniques. The methods share some common features. We discuss behavior of

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

for superconducting phases with s- and d-wave symmetry of the superconducting order parameter. In contrast to the mean-field treatment of U, we find that the strong on-site repulsion does not destroy superconductivity induced by ${\mathit{V}}_{\mathit{ij}}$0 even when U\ensuremath{\gg}|${\mathit{V}}_{\mathit{ij}}$|. \textcopyright{} 1996 The American Physical Society.