Spin-fluctuation mechanism of superconductivity

TL;DR

This paper models the superconductivity in cuprates using the extended t-J model, highlighting the dominant role of spin fluctuations and the influence of next-nearest-neighbor hopping t' on the critical temperature Tc.

Contribution

It introduces a theoretical framework linking spin fluctuations and next-nearest-neighbor hopping to superconductivity in cuprates, explaining Tc variations across different materials.

Findings

Superconductivity is primarily driven by spin fluctuations.

Tc depends strongly on the hopping parameter t'.

Abstract

Normal and superconducting state spectral properties of cuprates are theoretically described within the extended t-J model. The method is based on the equations of motion for projected fermionic operators and the mode-coupling approximation for the self-energy matrix. The dynamical spin susceptibility at various doping is considered as an input, extracted from experiments. The analysis shows that the onset of superconductivity is dominated by the spin-fluctuation contribution. The coupling to spin fluctuations directly involves the next-nearest-neighbor hopping t', hence Tc shows a pronounced dependence on t'. The latter can offer an explanation for the variation of Tc among different families of hole-doped cuprates. A formula for maximum Tc is given and it is shown that optimum doping, where maximum Tc is reached, is with increasing -t' progresively increased.