Date of Original Version
A zero-temperature renormalization group (RG) approach is applied to the one-dimensional, spin-112 anti ferromagnetic Heisenberg dimerized (alternating) chain. Specifically, the ground state energy and lowest-lying spectral excitations are examined. The calculation indicates the existence of a gap in the spectrum of the dimerized chain which vanishes only in the limit of a uniform spin chain. in contrast to a recent Green's function approach. The RG results are in reasonable agreement with numerical extrapolations on the exact eigenvalue spectrum of finite chains of up to 12 spins. Both methods are compared with several other approximate treatments of the Heisenberg system. and tested by comparison with exact results for the spin-112 XY dimerized chain.
J. N. Fields, H. W. J. Blöte, and J. C. Bonner. Renormalization group and other calculations for the one-dimenaional spin-1/2 dimerized Heisenberg antiferromagnet. J. Appl. Phys. 50 (1979), 1807.