Indications of spin-charge separation at short distance and stripe formation in the extended t-J model on ladders and planes - art. no. 014414

The recently discussed tendency of holes to generate nontrivial spin enviro nments in the extended two-dimensional t-J model [G. Martins, R. Eder, and E. Dagotto, Phys. Rev. B 60, R3716 (1999)] is here investigated using compu tational techniques applied to ladders with several number of legs. This te ndency is studied also with the help of analytic spin-polaron approaches di rectly in two dimensions. Our main result is that the presence of robust an tiferromagnetic correlations between spins located at both sides of a hole either along the x or y axis, observed before numerically on square cluster s, is also found using ladders, as well as applying techniques based on a s tring-basis expansion. This so-called "across-the-hole" nontrivial structur e exists even in the two-leg spin-gapped ladder system, and leads to an eff ective reduction in dimensionality and spin-charge separation at short-dist ances, with a concomitant drastic reduction in the quasiparticle weight Z. In general, it appears that holes tend to induce one-dimensional-like spin arrangements to improve their mobility. Using ladders it is also shown that the very small J/t similar to0.1 regime of the standard t-J model may be m ore realistic than anticipated in previous investigations, since such regim e shares several properties with those found in the extended model at reali stic couplings. Another goal of the present paper is to provide additional information on the recently discussed tendencies to stripe formation and sp in incommensurability reported for the extended t-J model. These tendencies are illustrated with several examples.