二维正方晶格Compass-XY模型的方向序和拓扑序

采用Monte Carlo方法研究二维正方晶格Compass-XY模型，通过调节过渡参量α，计算了降低交换相互作用的阻挫对方向序和拓扑序的影响.结果表明，方向序和拓扑序之间的转变是一个逐渐过渡的过程，并不存在明显的界限.在某一范围内，这两种序是相互重叠的，难以区分.阻挫的降低，易于形成拓扑序，同时会抑制方向序.当阻挫变得足够弱时，方向序被破坏.

Directional and Topological Orders in a Two-Dimensional Compass-XY Model on a Square Lattice

Two-dimensional Compass-XY model on a square lattice is investigated by means of Monte Carlo method. Effects of decreasing frustration of exchange interactions on directional and topological orders are studied by adjusting crossover parameter α. It is demonstrated that crossover between directional and topological orders is a gradual process,which means that there is no distinct barrier. Two kinds of ordering are partly overlapped within a certain range,making it difficult to tell them apart. Decrease of frustration facilitates topological order while suppressing directional order. Directional order may be destroyed as frustration is weak enough.