OPTICAL-ABSORPTION AND SINGLE-PARTICLE EXCITATIONS IN THE 2-DIMENSIONAL HOLSTEIN T-J MODEL

To discuss the interplay of electronic and lattice degrees of freedom in systems with strong Coulomb correlations we have performed an exten sive numerical study of the two-dimensional Holstein t-J model. The mo del describes the interaction of holes, doped in a quantum antiferroma gnet, with a dispersionsless optical phonon mode. We apply finite-latt ice Lanczos diagonalization, combined with a well-controlled phonon Hi lbert space truncation, to the Hamiltonian. The focus is on the dynami cal properties. In particular we have evaluated the single-particle sp ectral function and the optical conductivity for characteristic hole-p honon couplings, spin exchange interactions, and phonon frequencies. T he results are used to analyze the formation of lattice hole polarons in great detail. Links with experiments on layered perovskites are mad e. In addition, we compare the Chebyshev recursion and maximum entropy algorithms, used for calculating spectral functions, with standard La nczos methods.