Indications of spin-charge separation in the two-dimensional extended t-J model

The two-dimensional extended $t-J$ model is studied computationally in a broad region of parameter space, motivated by recent photoemission experiments for the undoped cuprate ${\mathrm{Ca}}_2{\mathrm{CuO}}_2{\mathrm{Cl}}_2$ [F. Ronning et al., Science 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 $(0,\pi )-(\pi ,0).\mathrm{}$ Studies with more holes show precursors of metallic stripe formation, with holes sharing their individual spin arrangements, and AF correlations generated across the stripe.