VARIATIONAL STATES FOR THE SPIN-PEIERLS SYSTEM

We introduce a family of Jastrow pair product states for quasi-one-dim ensional spin systems. Depending on a parameter they interpolate betwe en the resonating valence-bond ground state of the Haldane-Shastry mod el describing a spin liquid and the (dimerized) valence-bond solid gro und states of the Majumdar-Ghosh spin chain. These states are found to form an excellent basis for variational studies of Heisenberg chains with next-nearest-neighbor interactions and bond alternation as realiz ed in the spin-Peierls system CuGeO3.