Chinese Physics Letters
Yang-Lee Circle Theorem for an Antiferromagnetic Heisenberg Ladder
Xianzhi Wang
Abstract
The Yang-Lee zeros of an antiferromagnetic Heisenberg ladder model are determined. It is found that if J4≤0 Yang-Lee zeros are located on the unit circle and on the negative real axis in the complex activity plane. In particular, if J4≤0 and 2J2≥J4, Yang-Lee zeros are located on the unit circle and the Yang-Lee circle theorem is valid. If J4>0, Yang-Lee zeros are located on some complicated curves.