In order to identify the most favorable situation for superconductivity in the repulsive single-band Hubbard model, we have studied instabilities for d-wave pairing mediated by antiferromagnetic spin fluctuations and p-wave pairing mediated by ferromagnetic fluctuations with the fluctuation exchange approximation in both two dimensions and three dimensions. By systematically varying the band filling and band structure we have shown that (i) d pairing is stronger in two dimensions than in three dimensions and (ii) p pairing is much weaker than d pairing.In order to identify the most favorable situation for superconductivity in the repulsive single-band Hubbard model, we have studied instabilities for d-wave pairing mediated by antiferromagnetic spin fluctuations and p-wave pairing mediated by ferromagnetic fluctuations with the fluctuation exchange approximation in both two dimensions and three dimensions. By systematically varying the band filling and band structure we have shown that (i) d pairing is stronger in two dimensions than in three dimensions and (ii) p pairing is much weaker than d pairing.

arXiv:cond-mat/9909119Physical review. B, Condensed matterDec 1, 199976 citations

Effects of spin fluctuations in the t−J model

T. Obermeier, Thomas Pruschke, J. Keller

arXiv:cond-mat/9607037Physica B Condensed MatterFeb 1, 19971 citation

Heavy quasiparticles and Cooper-pair interaction in the Hubbard model

Fusayoshi J. Ohkawa

The Hubbard model is studied in the vicinity of the Mott transition. Local and quantal spin fluctuations are completely included through the mapping to the Anderson model; a local Kondo temperature ${T}_{K}$ is defined as their characteristic temperature or energy scale. Antiferromagnetic spin fluctuations are included perturbatively in terms of $\frac{1}{d}$ and to leading order in $\frac{{k}_{B}{T}_{K}}{U}$ with $d$ being the spatial dimensionality, ${k}_{B}$ the Boltzmann constant, and $U$ the intrasite repulsion. The two different kinds of spin fluctuations are responsible for the formation of heavy quasiparticles. Two intersite exchange interactions are responsible for both the development of the antiferromagnetic spin fluctuations and $d\ensuremath{\gamma}$-wave Cooper pairing between the heavy quasiparticles: the superexchange interaction and an exchange interaction due to the virtual exchange of spin excitations within the heavy quasiparticle band. An experimental specific-heat coefficient of about 14 mJ/ ${\mathrm{K}}^{2}$ Cu ${\mathrm{O}}_{2}$ mol and a Wilson ratio of about 0.4 imply that the interplay between the local and the antiferromagnetic spin fluctuations plays a crucial role in both the normal and the superconducting states of $\mathrm{Y}{\mathrm{Ba}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{7\ensuremath{-}\ensuremath{\delta}}$ with critical temperatures of ${T}_{c}\ensuremath{\simeq}90$ K. A pairing interaction deduced from the normal-state properties is strong enough to give critical temperatures as high as ${T}_{c0}\ensuremath{\simeq}200$ K in the absence of any pair breaking; there is experimental evidence that the pair-breaking effect of the antiferromagnetic spin fluctuations reduces ${T}_{c0}\ensuremath{\simeq}200$ K down to ${T}_{c0}\ensuremath{\simeq}90$ K.The Hubbard model is studied in the vicinity of the Mott transition. Local and quantal spin fluctuations are completely included through the mapping to the Anderson model; a local Kondo temperature ${T}_{K}$ is defined as their characteristic temperature or energy scale. Antiferromagnetic spin fluctuations are included perturbatively in terms of $\frac{1}{d}$ and to leading order in $\frac{{k}_{B}{T}_{K}}{U}$ with $d$ being the spatial dimensionality, ${k}_{B}$ the Boltzmann constant, and $U$ the intrasite repulsion. The two different kinds of spin fluctuations are responsible for the formation of heavy quasiparticles. Two intersite exchange interactions are responsible for both the development of the antiferromagnetic spin fluctuations and $d\ensuremath{\gamma}$-wave Cooper pairing between the heavy quasiparticles: the superexchange interaction and an exchange interaction due to the virtual exchange of spin excitations within the heavy quasiparticle band. An experimental specific-heat coefficient of about 14 mJ/${\mathrm{K}}^{2}$ Cu${\mathrm{O}}_{2}$ mol and a Wilson ratio of about 0.4 imply that the interplay between the local and the antiferromagnetic spin fluctuations plays a crucial role in both the normal and the superconducting states of $\mathrm{Y}{\mathrm{Ba}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{7\ensuremath{-}\ensuremath{\delta}}$ with critical temperatures of ${T}_{c}\ensuremath{\simeq}90$ K. A pairing interaction deduced from the normal-state properties is strong enough to give critical temperatures as high as ${T}_{c0}\ensuremath{\simeq}200$ K in the absence of any pair breaking; there is experimental evidence that the pair-breaking effect of the antiferromagnetic spin fluctuations reduces ${T}_{c0}\ensuremath{\simeq}200$ K down to ${T}_{c0}\ensuremath{\simeq}90$ K.

Physical review. B, Condensed matterDec 1, 19968 citations

Spin and charge fluctuations in the t–J model

George Jackeli, Nikolay M. Plakida

Physica B Condensed MatterJan 1, 19991 citation

Spin dynamics for the t-J model

Zhongbing Huang, Shiping Feng

arXiv:cond-mat/9805308Physics Letters AMay 1, 19985 citations

Pairing boost from enhanced spin-fermion coupling in the pseudogap regime

Yang Yu, Sergei Iskakov, Emanuel Gull +2 more

We perform a fluctuation analysis of the pairing interaction in the hole-doped Hubbard model within the dynamical cluster approximation. Our analysis reveals that spin-fluctuation-mediated pairing differs qualitatively in the over- and underdoped regimes. In the underdoped regime, spin fluctuations open a pseudogap. We show that in this regime the spin-fermion coupling mediates a giant attraction between antinodal fermions. This explains why superconductivity survives at underdoping in the Hubbard model and cuprates, despite the lack of coherent fermionic quasiparticles in the pseudogap regime.We perform a fluctuation analysis of the pairing interaction in the hole-doped Hubbard model within the dynamical cluster approximation. Our analysis reveals that spin-fluctuation-mediated pairing differs qualitatively in the over- and underdoped regimes. In the underdoped regime, spin fluctuations open a pseudogap. We show that in this regime the spin-fermion coupling mediates a giant attraction between antinodal fermions. This explains why superconductivity survives at underdoping in the Hubbard model and cuprates, despite the lack of coherent fermionic quasiparticles in the pseudogap regime.

arXiv:2410.01705Physical review. B./Physical review. BJun 16, 20253 citations

The Hubbard model is studied in the vicinity of the Mott transition. Local and quantal spin fluctuations are completely included through the mapping to the Anderson model; a local Kondo temperature

{T}_{K}

is defined as their characteristic temperature or energy scale. Antiferromagnetic spin fluctuations are included perturbatively in terms of

\frac{1}{d}

and to leading order in

\frac{{k}_{B}{T}_{K}}{U}

with

d

being the spatial dimensionality,

{k}_{B}

the Boltzmann constant, and

U

the intrasite repulsion. The two different kinds of spin fluctuations are responsible for the formation of heavy quasiparticles. Two intersite exchange interactions are responsible for both the development of the antiferromagnetic spin fluctuations and $d\ensuremath{\gamma}$-wave Cooper pairing between the heavy quasiparticles: the superexchange interaction and an exchange interaction due to the virtual exchange of spin excitations within the heavy quasiparticle band. An experimental specific-heat coefficient of about 14 mJ/

{\mathrm{K}}^{2}

{\mathrm{O}}_{2}

mol and a Wilson ratio of about 0.4 imply that the interplay between the local and the antiferromagnetic spin fluctuations plays a crucial role in both the normal and the superconducting states of $\mathrm{Y}{\mathrm{Ba}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{7\ensuremath{-}\ensuremath{\delta}}$ with critical temperatures of ${T}_{c}\ensuremath{\simeq}90$ K. A pairing interaction deduced from the normal-state properties is strong enough to give critical temperatures as high as ${T}_{c0}\ensuremath{\simeq}200$ K in the absence of any pair breaking; there is experimental evidence that the pair-breaking effect of the antiferromagnetic spin fluctuations reduces ${T}_{c0}\ensuremath{\simeq}200$ K down to ${T}_{c0}\ensuremath{\simeq}90$ K.