Indications of spin-charge separation in the two-dimensionalt-Jmodel

We have calculated the high temperature expansion for the density correlation function N(q) of the two-dimensional t-J model. On extrapolation by Padé approximants to low temperatures we find that N(q) has 2${\mathbf{k}}_{\mathit{F}}^{\mathrm{SF}}$ as a characteristic wave vector. Previous studies have shown that ${\mathit{n}}_{\mathbf{k}}$ has a steplike feature at ${\mathbf{k}}_{\mathit{F}}$ and S(q) has 2${\mathbf{k}}_{\mathit{F}}$ as a characteristic wave vector. Here ${\mathit{k}}_{\mathit{F}}$ and ${\mathit{k}}_{\mathit{F}}^{\mathrm{SF}}$ are the Fermi wave vectors of the nearest-neighbor square lattice tight-binding and spinless fermion models, respectively. By comparison to known results for one dimension this suggests spin-charge separation in the two-dimensional t-J model.