Effective theory of the hole-doped spin-1 chain

An effective theory for the hole-doped spin-1 antiferromagnetic chain is proposed in this paper. The two branches of low-energy quasiparticle excitation is obtained by the diagrammatic technique. In the large t limit (in which t is the hole hopping term), the lower band is essentially the bound state of one hole and one magnon and the other band is the single-hole state. We find a critical value of t, t(c) = 0.21 Delta(H) (in which Delta(H) is the Haldane gap). For t > t(c), with the decrement of t, the mixing of these two bands become stronger and stronger, and at the same time the effective band mass becomes larger and larger. When t < t(c) the minimum of the lower band moves away from zero to the other point between zero and pi/2. The spin structure factor is also calculated in this paper, and we find that for the large t Limit the main contribution is from the interband transition, which induces a resonant peak in the Haldane gap. For the small t limit the main contribution is from the intraband transition, which only causes a diffusionlike broad bump in the Haldane gap. [S0163-1829(99)03817-5].