Superconductivity in the bilayer Hubbard model: Are two Fermi surfaces better than one?

Abstract

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 $t_{\perp }$, using many-body perturbation theory and variational methods. They have generally found that superconductivity is enhanced as one of the bands approaches the Liftshiz 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 $s_{\pm }$ pairing correlations in the large $t_{\perp }$ 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 $T_c$. 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.

arXiv comment13 pages, 13 figures

References in corpus (31)

• Unconventional sign-reversing superconductivity in LaFeAsO_(1-x)F_x
• Unconventional pairing originating from disconnected Fermi surfaces in superconducting LaFeAsO${}_{1-x}$F${}_x$}
• Quantum Cluster Theories
• Interface induced high temperature superconductivity in single unit-cell FeSe films on SrTiO3
• Phase Diagram and High Temperature Superconductivity at 65 K in Tuning Carrier Concentration of Single-Layer FeSe Films
• Interfacial mode coupling as the origin of the enhancement of Tc in FeSe films on SrTiO3
• Pressure evolution of low-temperature crystal structure and bonding of 37 K $T_c$ FeSe superconductor
• Enhancement of superconducting transition temperature of FeSe by intercalation of a molecular spacer layer
• Phonon-enhanced superconductivity at the FeSe/SrTiO3 interface
• Critical role of substrate in the high temperature superconductivity of single layer FeSe on Nb:BaTiO${}_3$
• A Quantum Monte Carlo algorithm for non-local corrections to the Dynamical Mean-Field Approximation
• Origin of Gap Anisotropy in Spin Fluctuation Models of the Fe-pnictides
• Observation of Double-Dome Superconductivity in Potassium-Doped FeSe Thin Films
• The Structure of the Pairing Interaction in the 2D Hubbard Model
• Influence of microstructure on superconductivity in K${}_x$Fe${}_{2-y}$Se${}_2$ and evidence for a new parent phase K${}_2$Fe${}_7$Se${}_8$
• High-temperature superconductivity in single-unit-cell FeSe films on anatase TiO2(001)
• Competing magnetic orders in a bilayer Hubbard model with ultracold atoms
• Electron pairing in the presence of incipient bands in iron-based superconductors
• Sub-matrix updates for the Continuous-Time Auxiliary Field algorithm
• Orbital coupling and superconductivity in the iron pnictides
• High Tc via spin fluctuations from incipient bands: application to monolayers and intercalates of FeSe
• How correlated is the FeSe/SrTiO${}_3$ system ?
• Evolution of spin excitations from bulk to monolayer FeSe
• Shadow gap in the over-doped (Ba${}_{1-x}$K${}_x$)Fe${}_2$As${}_2$ compound
• Multiband full-bandwidth anisotropic Eliashberg theory of interfacial electron-phonon coupling and high-T${}_c$ superconductivity in FeSe/SrTiO${}_3$
• Effective pairing interaction in a system with an incipient band
• DCA++: A software framework to solve correlated electron problems with modern quantum cluster methods
• The overdoped end of the cuprate phase diagram
• Proposal for a bulk material based on a monolayer FeSe on SrTiO3 high-temperature superconductor
• Enhanced superconductivity in FeSe/SrTiO${}_3$ from the combination of forward scattering phonons and spin fluctuations
• Cooper Pairing in Insulating Valence Band in Fe-Based Superconductors