On the theory of the spin gap in bilayer cuprates

loffe L.B., Larkin A.I., Millis A.J., Altshuler B.L.

\ **We formulate and solve a model of two planes of antiferromagneticaUy correlated electrons coupled together by a weak antiferromagnetic interaction of strength λ. We show that in-plane antiferromagnetic correlations dramatically enhance the pairing effect of the interplane interaction. For the case where the in-plane correlation length κ~' ~ T*""**^{1}/^{2}, we find that the interaction λ leads to spin pairing at α temperature *τ* ~ x, ***much higher than the usual BCS result exp(—J/λ). We suggest that this is a possible explanation of the spin gap effects observed below ***t* ***~'150K in YBa**_{2}Cu_{3}0_{6}.6.