Date of Award
Doctor of Philosophy
Dr. Sung G. Chung
In this dissertation, we use the recently developed Entanglement Perturbation Theory (EPT) to solve antiferromagnetic spin chain problems, for both spin 1/2 and spin 1. We firs use EPT-g (EPT algorithm for ground state) to get the ground state properties. We calculated precisely energies, magnetization and spin-spin correlations. The precision of the long range spin-spin correlation functions for spin 1/2 chains is unprecedented. Due to its special structure, we also use EPT-g to calculate the firs excited state properties for spin 1 chains. Hence we plotted the phase diagram for spin 1 xxz chains. Also a generalization of EPT (EPT-e) for elementary excitation in one dimension determined the spin-triplet magnon spectrum for spin 1 chain for the firs time for the entire Brillouin zone, including the Haldane gap at k = π. The spin chains, the 2D&3D Ising models, the 1D&2D Hubbard models and the Bose-Hubbard model whose study by EPT is recently started represent a variety of strongly correlated many body systems with translational symmetry. Namely EPT is a general method for them. On the other hand, the successful application of EPT-e indicates EPT's potential to study the inhomogeneous quantum systems.
Wang, Lihua, "Entanglement Perturbation Theory for Antiferromagnetic Spin Chains" (2009). Dissertations. 699.