4.6 Article

Superconductivity in the bilayer Hubbard model: Two Fermi surfaces are better than one

期刊

PHYSICAL REVIEW B
卷 104, 期 24, 页码 -

出版社

AMER PHYSICAL SOC
DOI: 10.1103/PhysRevB.104.245109

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资金

  1. Ad-vanced Computing (SciDAC) program - U.S. Department of Energy, Office of Science, Advanced Scientific Computing Research and Basic Energy Sciences, Division of Materials Sciences and Engineering
  2. U.S. Department of Energy, Office of Basic Energy Sciences, Materials Sciences and Engineering Division
  3. DOE Office of Science User Facility [DE-AC05-00OR22725]
  4. U.S. Department of Energy [DE-AC0500OR22725]

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Research on the bilayer Hubbard model has shown that robust s +/- pairing correlations exist in the model, especially in the large t perpendicular limit, when one band becomes incipient. However, this behavior is counteracted by a suppression of the intrinsic pair-field susceptibility and does not result in an increased critical temperature.
Fully occupied or unoccupied bands in a solid are often considered inert and irrelevant to a material's low-energy properties. But the discovery of enhanced superconductivity in heavily electron-doped FeSe-derived superconductors poses questions about the possible role of incipient bands (those laying close to but not crossing the Fermi level) in pairing. To answer this question, researchers have studied pairing correlations in the bilayer Hubbard model, which has an incipient band for large interlayer hopping t perpendicular to, using many-body perturbation theory and variational methods. They have generally found that superconductivity is enhanced as one of the bands approaches the Lifshitz transition and even when it becomes incipient. Here we address this question using the nonperturbative quantum Monte Carlo (QMC) dynamical cluster approximation (DCA) to study the bilayer Hubbard model's pairing correlations. We find that the model has robust s +/- pairing correlations in the large t perpendicular to limit, which can become stronger as one band is made incipient. While this behavior is linked to changes in the effective interaction, we further find that it is counteracted by a suppression of the intrinsic pair-field susceptibility and does not translate to an increased Tc. Our results demonstrate that the highest achievable transition temperatures in the bilayer Hubbard model occur when the system has two bands crossing the Fermi level.

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