Pairing Mechanism of the Heavily Electron Doped FeSe Systems: Dynamical Tuning of the Pairing Cutoff Energy

Abstract

We studied pairing mechanism of the heavily electron doped FeSe (HEDIS) systems, which commonly have one incipient hole band -- a band top below the Fermi level by a finite energy distance ${\epsilon }_b$ -- at $\Gamma$ point and ordinary electron bands at $M$ points in Brillouin zone (BZ). We found that the system allows two degenerate superconducting solutions with the exactly same $T_c$ in clean limit: the incipient $s_{he}^{\pm }$-gap (${\Delta }_h^{-}\ne 0$, ${\Delta }_e^{+}\ne 0$) and $s_{ee}^{++}$-gap (${\Delta }_h=0$, ${\Delta }_e^{+}\ne 0$) solutions with different pairing cutoffs, ${\Lambda }_{sf}$ (spin fluctuation energy) and ${\epsilon }_b$, respectively. The $s_{ee}^{++}$-gap solution, in which the system dynamically renormalizes the original pairing cutoff ${\Lambda }_{sf}$ to ${\Lambda }_{phys}={\epsilon }_b$ ($<{\Lambda }_{sf}$), therefore actively eliminates the incipient hole band from forming Cooper pairs, but without loss of $T_c$, becomes immune to the impurity pair-breaking. As a result, the HEDIS systems, by dynamically tuning the pairing cutoff and selecting the $s_{ee}^{++}$-pairing state, can always achieve the maximum $T_c$ -- the $T_c$ of the degenerate $s_{he}^{\pm }$ solution in the ideal clean limit -- latent in the original pairing interactions, even in dirty limit.

12 pages, 11 figures; Appendix A is added

References in corpus (10)

• Superconductivity in single-layer films of FeSe with a transition temperature above 100 K
• Heavily electron-doped electronic structure and isotropic superconducting gap in AxFe2Se2 (A=K,Cs)
• Structure determination and coexistence of superconductivity and antiferromagnetic order in (Li0.8Fe0.2)OHFeSe
• Superconductivity at 32 K in single crystal Rb${}_{0.78}$Fe${}_2$Se${}_{1.78}$}
• Superfluid density of the $\pm$s-wave state for the iron-based superconductors
• Suppression of superconductivity by Neel-type magnetic fluctuations in the iron pnictides
• Unexpected impact of magnetic disorder on multiband superconductivity
• Manifestation of impurity induced s_{+-} -> s_{++} transition: multiband model for dynamical response functions
• Isotope effect and the role of phonon in the Fe-based superconductors
• Effects of phonon interaction on the pairing in the high-T$c$ superconductors

Cited by in corpus (16)

• Possible high $T_c$ Superconductivity in La${}_3$Ni${}_2$O${}_7$ under High Pressure through Manifestation of a Nearly-Half-Filled Bilayer Hubbard Model
• Finite energy spin fluctuation as a pairing glue in systems with coexisting electron and hole bands
• Wide applicability of high $T_c$ pairing originating from coexisting wide and incipient narrow bands in quasi one dimension
• Superconducting mechanism for the cuprate Ba${}_2$CuO${}_{3+\delta }$ based on a multiorbital Lieb lattice model
• Strongly enhanced superconductivity due to finite energy spin fluctuations induced by an incipient band : a FLEX study on the bilayer Hubbard model with vertical and diagonal interlayer hoppings
• Possible high-$T_c$ superconductivity due to incipient narrow bands originating from hidden ladders in Ruddlesden-Popper compounds
• Many-variable variational Monte-Carlo study of superconductivity in two-band Hubbard models with an incipient band
• Resonant pair-exchange scattering and BCS-BEC crossover in a system composed of dispersive and heavy incipient bands: a Feshbach analogy
• Phonon Boost Effect on the $S^{\pm }$-wave Superconductor with Incipient Band
• Designing nickelate superconductors with $d^8$ configuration exploiting mixed-anion strategy
• Possible counterintuitive enhancement of superconductivity in ladder-type cuprates by longitudinal compression
• Hidden robust presence of a hole Fermi surface in a heavily electron doped iron based superconductor LaFe${}_2$As${}_2$
• Possible spin excitation structure in monolayer FeSe grown on SrTiO${}_3$
• Theoretical study of spin-fluctuation-mediated superconductivity in two-dimensional Hubbard models with an incipient flat band
• In-gap bound states induced by a single nonmagnetic impurity in sign-preserving s-wave superconductors with incipient bands
• Hidden Ladder in SrMoO${}_3$/SrTiO${}_3$ Superlattices: Experiments and Theoretical Calculations