Physical Review B
Phase transition of S=12 two-leg Heisenberg spin ladder systems with a four-spin interaction
Keigo Hijii, K. Nomura
Abstract
We study a phase transition and critical properties of the quantum spin ladder system with a four-spin interaction. We determine a phase boundary between a rung singlet and a staggered dimer phases numerically. This phase transition is of a second order in the weak-coupling region. We confirm that this universality class is described by the $k=2$ SU(2) Wess-Zumino-Witten model, analyzing the central charge and scaling dimensions. In the strong-coupling region, phase transition becomes of a first order.