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 YBa2Cu306.6.