Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Strasse 1, D-85748 Garching, Germany.
Institut für Quanteninformation, RWTH Aachen University, D-52056 Aachen, Germany.
Phys Rev Lett. 2014 Jan 24;112(3):036402. doi: 10.1103/PhysRevLett.112.036402. Epub 2014 Jan 23.
We analyze the low energy excitations of spin lattice systems in two dimensions at zero temperature within the framework of projected entangled pair state models. Perturbations in the bulk give rise to physical excitations located at the edge. We identify the corresponding degrees of freedom, give a procedure to derive the edge Hamiltonian, and illustrate that it can exhibit a rich phase diagram. For topological models, the edge Hamiltonian is constrained by the topological order in the bulk, which gives rise to one-dimensional edge models with unconventional properties; for instance, a topologically ordered bulk can protect a ferromagnetic Ising chain at the edge against spontaneous symmetry breaking.
我们在投影纠缠对态模型的框架内分析了二维零温下自旋晶格系统的低能激发。体中的微扰导致位于边缘的物理激发。我们确定了相应的自由度，给出了导出边缘哈密顿量的方法，并说明了它可以表现出丰富的相图。对于拓扑模型，边缘哈密顿量受到体中拓扑序的约束，这导致具有非平凡性质的一维边缘模型；例如，拓扑有序的体可以保护边缘的铁磁伊辛链免受自发对称破缺的影响。
