THEORY OF THE DENSITY FLUCTUATION SPECTRUM OF STRONGLY CORRELATED ELECTRONS

The density response function N(q,omega) of the two-dimensional t-J mo del is studied starting from a mixed-gauge formulation of the slave-bo son approach. Our results for N(q,omega) are in remarkable agreement w ith exact diagonalization studies, and provide a natural explanation o f the anomalous features in the density response in terms of the spin- polaron nature of the charge carriers. In particular, we have identifi ed unexplained low-energy structures in the diagonalization data as ar ising from the coherent polaron motion of holes in a spin liquid.