On the theory of superconductivity in the extended Hubbard model

We study d-wave superconductivity in the extended Hubbard model in the strong correlation limit for a large intersite Coulomb repulsion V . We argue that in the Mott-Hubbard regime with two Hubbard subbands there emerges a new energy scale for the spin-fluctuation coupling of electrons of the order of the electronic kinetic energy W much larger than the exchange energy J. This coupling is induced by the kinematic interaction for the Hubbard operators which results in the kinematic spinfluctuation pairing mechanism for V W . The theory is based on the Mori projection technique in the equation of motion method for the Green functions in terms of the Hubbard operators. The doping dependence of superconductivity temperature Tc is calculated for various values of U and V .

“…As described in detail in Refs. [18,22], using the Mori-type projection method [20] we derive an exact representation for the GF (13) in the form of the Dyson equation…”

Section: B Green Functionsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Kinematic spin-fluctuation mechanism of high-temperature superconductivity

Плакида

Oudovenko

2014

“…One of the scenarios of the development of the theory is associated with the use of the atomic representation [72] and diagram technique for the Hubbard operators [73]. The models in which the Kohn-Luttinger renormalizations can be taken into account include the generalized t − J − V model [74][75][76] and the t − J * − V model with three-center interactions (the important role of such interactions in describing the superconducting state was studied in [77][78][79][80][81][82][83][84]). These models are effective low-energy versions of the ShubinVonsovsky model.…”

Section: T − J Modelmentioning

confidence: 99%

The Kohn-Luttinger effect and anomalous pairing in new superconducting systems and graphene

Kagan

Вальков

Mitskan

et al. 2014

We present a review of theoretical investigations into the Kohn-Luttinger nonphonon superconductivity mechanism in various 3D and 2D repulsive electron systems described by the Fermi-gas, Hubbard, and Shubin-Vonsovsky models. Phase diagrams of the superconducting state are considered, including regions of anomalous s−, p−, and d−wave pairing. The possibility of a strong increase in the superconducting transition temperature Tc even for a low electron density is demonstrated by analyzing the spin-polarized case or the two-band situation. The Kohn-Luttinger theory explains or predicts superconductivity in various materials such as heterostructures and semimetals, superlattices and dichalcogenides, high-Tc superconductors and heavy-fermion systems, layered organic superconductors, and ultracold Fermi gases in magnetic traps. This theory also describes the anomalous electron transport and peculiar polaron effects in the normal state of these systems. The theory can be useful for explaining the origin of superconductivity and orbital currents (chiral anomaly) in systems with the Dirac spectrum of electrons, including superfluid 3 He-A, doped graphene, and topological superconductors.

“…As a result, the contributions associated with the electron-phonon, spin-fluctuation, and charge-fluctuations contributions [25,26] had to be taken into account additionally to compensate the strong repulsion associated with the intersite Coulomb interaction of holes. It should be noted, however, that the Coulomb interaction potential between holes in different cells was chosen in [25,26] equal to V = 0.2 eV, which is much lower than the spinfluctuation pairing potential g sf = 1.5 eV caused by the kinematic interaction; it is only for this reason that the superconducting d-wave phase was preserved. Due to a stronger kinematic mechanism [4], Cooper pairing was also observed at comparatively high values of V .…”

Section: Introductionmentioning

confidence: 99%

Coulomb repulsion of holes and competition between $${d_{{x^2} - {y^2}}}$$ d x 2 − y 2 -wave and s-wave parings in cuprate superconductors

Вальков

Dzebisashvili

Korovushkin

et al. 2017

The effect of the Coulomb repulsion of holes on the Cooper instability in an ensemble of spin-polaron quasiparticles has been analyzed, taking into account the peculiarities of the crystallographic structure of the CuO2 plane, which are associated with the presence of two oxygen ions and one copper ion in the unit cell, as well as the strong spinfermion coupling. The investigation of the possibility of implementation superconducting phases with d-wave and s-wave pairing of the order parameter symmetry has shown that in the entire doping region only the d-wave pairing satisfies the self-consistency equations, while there is no solution for the s-wave pairing. This result completely corresponds to the experimental data on cuprate HTSC. It has been demonstrated analytically that the intersite Coulomb interaction does not affect the superconducting d-wave pairing, because its Fourier transform Vq does not appear in the kernel of the corresponding integral equation.