Topological Phase Transition in the Extended Cluster Compass Ladder

We have studied the exact solution of the extended cluster compass ladder, which is equivalent to extended quantum compass model with cluster interaction between next-nearest-neighbor spins, by using the Jordan-Wigner transformation. We show that this model is always gapfull except at the critical surfaces where the energy gap disappears. We obtain the analytic expressions of all critical couplings which drive quantum phase transitions. This model shows a rich phase diagram which includes spin-flop, strip antiferromagnetic and topological ordered on the legs, in addition to the phase with antiparallel ordering of spin y component on the rungs. We study also the universality and scaling properties of the three point correlation functions derivatives in different regions to confirm the results obtained using the energy gap analysis. On the other hand, we have replaced the cluster interaction with usual form and using the Lanczos method a numerical experiment is done. Analyzing the numerical results, we show that the effect of the cluster interaction between next-nearest-neighbor spins is completely different from the usual form. PACS numbers: 75.10.Pq, 64.70.Tg, 03.67.Mn, 75.10.Jm I