Order from disorder: Nonmagnetic impurities in the spin-gap phase of the cuprates

We solve the problem of N nonmagnetic impurities in the staggered flux phase of the Heisenberq model which we assume to be a good mean-field approximation for the spin-gap phase of the cuprates. The density of states is evaluated exactly in the unitary scattering limit and is proportional to 1/omega 1n(2)(\w\/D), in analogy with the 1D case of doped spin-Peierls and two-leg ladder compounds. We argue that the system exhibits a quasi-long-range order at T = 0 with instantaneous spin-spin correlations decreasing as n(1)/1n(2)(n(i)R(ij)) for large distances R-ij and we predict enhanced low energy fluctuations in neutron scattering. [S0031-9007(98)06907-5].