Gauge Theory Description of Spin Chains and Ladders
Abstract
Description
An S=1/2 anti-ferromagnetic spin chain is mapped to the two-flavor massless Schwinger model, which admits a gapless mode. In a spin ladder system rung interactions break the chiral invariance. These systems are solved by bosonization. If the number of legs in a cyclically symmetric ladder system is even, all of the gapless modes of spin chains become gapful. However, if the number of legs is odd, one combination of the gapless modes remains gapless. For a two-leg system we find that the spin gap is about .36 |J'| when the inter-chain Heisenberg coupling J' is small compared with the intra-chain Heisenberg coupling.
4 pages. To appear in the Proceedings of SOLITONS, a CRM-Fields-CAP Summer Workshop in Theoretical Physics, July 20 - July 26, 1997, Kingston, Ontario, Canada. (Springer-Verlag)
4 pages. To appear in the Proceedings of SOLITONS, a CRM-Fields-CAP Summer Workshop in Theoretical Physics, July 20 - July 26, 1997, Kingston, Ontario, Canada. (Springer-Verlag)