Magnetization plateau in the spin ladder with the four-spin exchange
Abstract
The magnetization process of the
S
=1/2 antiferromagnetic spin ladder with the four-spin cyclic exchange interaction at T=0 is studied by the exact diagonalization of finite clusters and size scaling analyses. It is found that a magnetization plateau appears at half the saturation value if the ratio of the four- and two-spin exchange coupling constants
J
4
is larger than the critical value
J
4c
=0.05±
0.04. The phase transition with respect to
J
4
at
J
4c
is revealed to be the Kosterlitz-Thouless-type.