Theoretical Study of Electron Correlation Driven Superconductivity in Systems with Coexisting Wide and Narrow Bands

Ogura, Daisuke

doi:10.1007/978-981-15-0667-3

Cited by 9 publications

(11 citation statements)

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“…This can be understood as follows. In ref., 27) it was revealed using FLEX that the portion of the bonding band close to the Fermi level is strongly renormalized due to electron correlation to give a DOS schematically depicted in Fig.9(b). This effect is also seen in a dynamic cluster quantum Monte Carlo study for the bilayer Hubbard model without t ′ .…”

Section: Discussionmentioning

confidence: 99%

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

2020

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We study the spin-fluctuation-mediated s±-wave superconductivity in the bilayer Hubbard model with vertical and diagonal interlayer hoppings. As in the two-leg ladder model with diagonal hoppings, studied previously by the present authors, superconductivity is strongly enhanced when one of the bands lies just below (or touches) the Fermi level, that is, when the band is incipient. The strong enhancement of superconductivity is because large weight of the spin fluctuations lies in an appropriate energy range, whereas the low energy, pair-breaking spin fluctuations are suppressed. The optimized eigenvalue of the linearized Eliashberg equation, a measure for the strength of superconductivity, is not strongly affected by the bare width of the incipient band, but the parameter regime where superconductivity is optimized is wide when the incipient band is narrow, and in this sense, the coexistence of narrow and wide bands is favorable for superconductivity.

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Section: Discussionmentioning

confidence: 99%

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

2020

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“…Recently, such a band lying just above or below the Fermi level is referred to as an "incipient band" and has received attention, especially in the context of the iron-based superconductors [27][28][29][30][31][32][33][34][35]38], where hole bands lying just below the Fermi level are observed in some materials [30,31,[68][69][70][71][72][73][74][75]. In a wider context, the possibility of the occurrence or strong enhancement of superconductivity due to an incipient band has long been proposed for multiband Hubbard models on various types of lattices [23,26,36,37,[39][40][41][42][43][44][76][77][78][79][80][81][82]. A salient feature in these cases is that the gap function typically exhibits nodeless "s±-wave" symmetry.…”

Section: Dependence On the Level Offset Between The Two Orbitalsmentioning

confidence: 99%

Superconducting mechanism for the cuprate Ba2CuO3+δ based on a multiorbital Lieb lattice model

Yamazaki

Ochi

Ogura

et al. 2020

Phys. Rev. Research

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For the recently discovered cuprate superconductor Ba 2 CuO 3+δ , we propose a lattice structure which resembles the model considered by Lieb to represent the vastly oxygen-deficient material. We first investigate the stability of the Lieb-lattice structure and then construct a multiorbital Hubbard model based on first-principles calculation. By applying the fluctuation-exchange approximation to the model and solving the linearized Eliashberg equation, we show that s-wave and d-wave pairings closely compete with each other and, more interestingly, that the intraorbital and interorbital pairings coexist. We further show that if the energy of the d 3z 2 −r 2 band is raised to make it "incipient" with the lower edge of the band close to the Fermi level within a realistic band filling regime, s±-wave superconductivity is strongly enhanced. We reveal an intriguing relation between the Lieb model and the two-orbital model for the usual K 2 NiF 4 structure where a close competition between sand d-wave pairings is known to occur. The enhanced superconductivity in the present model is further shown to be related to an enhancement found previously in the bilayer Hubbard model with an incipient band.

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“…Recently, such a band lying just above or below the Fermi level is referred to as an "incipient band", and has received attention especially in the context of the iron-based superconductors [27][28][29][30][31][32][33][34][35]38], where hole bands lying just below the Fermi level is observed in some materials [62][63][64][65][66][67][68][69][70][71]. In a wider context, possibility of the occurrence or strong enhancement of superconductivity due to an incipient band has long been proposed for multiband Hubbard models on various types of lattices [23,26,36,37,[39][40][41][42][43][44][72][73][74][75][76][77][78]. A salient feature in these cases is that the gap function typically exhibits nodeless "s±-wave" symmetry.…”

Section: Dependence On the Level Offset Between The Two Orbitalsmentioning

confidence: 99%

Superconducting mechanism for the cuprate Ba$_2$CuO$_{3+δ}$ based on a multiorbital Lieb lattice model

Yamazaki,

Ochi,

Ogura

et al. 2020

Preprint

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For a recently discovered new-type cuprate superconductor Ba2CuO 3+δ , we propose a lattice structure which resembles the model considered by Lieb to represent the vastly oxygen-deficient material. We first investigate the stability of the Lieb-lattice structure, and then construct a multiorbital Hubbard model based on first-principles calculation. By applying the fluctuation-exchange approximation to the model and solving the linearized Eliashberg equation, we show that s-wave and d-wave pairings closely compete with each other, and, more interestingly, that the intra-orbital and inter-orbital pairings coexist. We further show that, if the energy of the d 3z 2 −r 2 band is raised to make it "incipient" with the lower edge of the band close to the Fermi level within a realistic band filling regime, s±-wave superconductivity is strongly enhanced. We reveal an intriguing relation between the Lieb model and the two-orbital model for the usual K2NiF4 structure where a close competition between s− and d−wave pairings is known to occur. The enhanced superconductivity in the present model is further shown to be related to an enhancement found previously in the bilayer Hubbard model with an incipient band.

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Theoretical Study of Electron Correlation Driven Superconductivity in Systems with Coexisting Wide and Narrow Bands

Cited by 9 publications

References 0 publications

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

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

Superconducting mechanism for the cuprate Ba2CuO3+δ based on a multiorbital Lieb lattice model

Superconducting mechanism for the cuprate Ba$_2$CuO$_{3+δ}$ based on a multiorbital Lieb lattice model

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