Abstract
We study the low-energy excitations of the spin- antiferromagnetic Heisenberg chain and -leg ladders in a staggered magnetic field . We show that induces gap and midgap states in all the cases and we will examine their field scaling behavior. A modified boundary scheme is devised to extract accurate bulk excitation behavior. The gap values converge rapidly as increases, leading to a field scaling exponent for both the longitudinal and transverse gaps of the square lattice . The midgap states induced by the boundary edge effects share the bulk gap scaling exponents but their overall scaling behavior in the large- limit needs further investigation.
- Received 25 July 2005
DOI:https://doi.org/10.1103/PhysRevB.73.012411
©2006 American Physical Society