Eur. Phys. J. B 55, 371-376 (2007)
https://doi.org/10.1140/epjb/e2007-00068-8

Scaling behaviour of the energy gap of spin-1/2 AF-Heisenberg chains in both uniform and staggered fields

Institute for Advanced Studies in Basic Sciences, Zanjan, 45195-1159, Iran

Corresponding author: ^a mahdavifar@iasbs.ac.ir

Received: 24 August 2006
Revised: 8 January 2006
Published online: 9 March 2007

Abstract

The energy gap of the 1D AF-Heisenberg model in the presence of both uniform (H) and staggered (h) magnetic fields is investigated using the exact diagonalization technique. The opening of the gap in the presence of a staggered field is found to scale with h^ν, where ν=ν(H) is the critical exponent, and depends on the uniform field. With respect to the range of the staggered magnetic field, two regimes are identified through which the dependence of the real critical exponent ν(H) on H can be calculated numerically. Our numerical results are in good agreement with the results obtained by other theoretical approaches.