Indications of Spin-Charge Separation in the 2D Extended t-J Model

The 2D extended $\rm t-J$ model is studied computationally in a broad region of parameter space, motivated by recent photoemission experiments for the undoped cuprate $\rm Ca_2 Cu O_2 Cl_2$ (F. Ronning et al., Science {\bf 282}, 2067 (1998)). The one-hole ground state is shown to develop robust antiferromagnetic (AF) correlations between spins separated by the mobile hole (i.e. across the hole). This effect tends to decouple charge from spin, and the quasiparticle weight becomes negligible, particularly at momenta $(0,\pi)-(\pi,0)$. Studies with more holes show precursors of metallic stripe formation, with holes sharing their individual spin arrangements, and AF-correlations generated across the stripe.