Spin and Charge Excitations in the Two-Dimensional t-J Model: Comparison with Fermi and Bose Systems

Using high temperature series we calculate temperature derivatives of the spin-spin and density-density correlation functions to investigate the low energy spin and charge excitations of the two-dimensional t-J model. We find that the temperature derivatives indicate different momentum dependences for the low energy spin and charge excitations. By comparing short distance density-density correlation functions with those of spinless fermions and hard core bosons, we find that the t-J model results are intermediate between the two cases, being closer to those of hard core bosons. The implications of these results for superconductivity are discussed.