Finite size properties of staggered [formula omitted] superspin chains

Abstract

Based on the exact solution of the eigenvalue problem for the U q [ sl ( 2 | 1 ) ] vertex model built from alternating three-dimensional fundamental and dual representations by means of the algebraic Bethe ansatz we investigate the ground state and low energy excitations of the corresponding mixed superspin chain for deformation parameter q = exp ( − i γ / 2 ) . The model has a line of critical points with central charge c = 0 and continua of conformal dimensions grouped into sectors with γ-dependent lower edges for 0 ⩽ γ < π / 2 . The finite size scaling behavior is consistent with a low energy effective theory consisting of one compact and one non-compact bosonic degree of freedom. In the ‘ferromagnetic’ regime π < γ ⩽ 2 π the critical theory has c = − 1 with exponents varying continuously with the deformation parameter. Spin and charge degrees of freedom are separated in the finite size spectrum which coincides with that of the U q [ osp ( 2 | 2 ) ] spin chain. In the intermediate regime π / 2 < γ < π the finite size scaling of the ground state energy depends on the deformation parameter.