  Finding new topological materials and understanding the physical essence of
topology are crucial problems for researchers. We studied the topological
property based on several proposed Su-Schrieffer-Heeger (SSH) related models.
We show that the topologically non-trivial phase (TNP) in the SSH model can
exist in other model conditions and can even be caused by anisotropy; its
origin has a close relation with the even-bond dimerization. Further study
shows that the TNP is not determined by the periodicity of the system, but the
parity of the two kinds of bonds plays a significant role for the formation of
the TNP. This finding reveals the topological invariant of the system and might
supply potential extended topological materials for both theoretical and
experimental researches.
