Stripes disorder and correlation lengths in doped antiferromagnets

For stripes in doped antiferromagnets, we find that the ratio of spin and charge correlation lengths xi (s)/xi (c) provides a sharp criterion for determining the dominant form of disorder in the system. If stripes are disordered predominantly by topological defects then xis(/)xi (c)less than or similar to1. In contast, if stripes correlations are disordered primarily by nontopological elastic deformations (i.e., a Bragg-glass type of disorder) then 1<(s)/xi (c)less than or similar to4 is expected. Therefore, the observation of xi (s)/xi (c)approximate to4 in (LaNd)(2-x)SrxCuO4 and xi (s)/xi (c)approximate to3 in La2/3Sr1/3NiO4 invariably implies that the stripes are in a Bragg-glass-type state, and topological defects are much less relevant than commonly assumed. Expected spectral properties are discussed. Thus, we establish the basis for any theoretical analysis of the experimentally observed glassy state in these materials.