Effect of correlated disorder on the temperature of unconventional cooper pairing: 3He in aerogel

It has been shown by the example of ³He in aerogel that the correlation in the position of impurities may have a considerable effect on the transition temperature T _c of a Fermi fluid to an unconventional superfluid or superconducting state if the correlation radius of the system of impurities exceeds the correlation length ξ₀ of the emerging superfluid phase. A decrease in T _c of ³He in aerogel has been expressed in terms of the structure factor of aerogel. Taking into account the fractal structure of aerogel provides a simple formula that satisfactorily describes the observed decrease in T _c.