Heisenberg spin-1 chain in a staggered magnetic field: A density-matrix-renormalization-group study

Using the density-matrix-renormalization-group technique, we calculate nume rically the low-energy excitation spectrum and magnetization curve of the s pin-1 antiferromagnetic chain in a staggered magnetic field, which is expec ted to describe the physics of the R2BaNiO5 (R not equal Y) family below th e Neel temperature of the magnetic rare-earth (Rf sublattice. These results are valid in the entire range of the staggered field, and agree with those given by the nonlinear sigma model study for small fields, but differ from the latter for large fields. They are consistent with the available experi mental data. The correlation functions for this model are also calculated. The transverse correlations display the anticipated exponential decay with- shorter correlation length, while the: longitudinal correlations show expli citly the induced staggered magnetization. [S0163-1829(99)04021-7].