Lycée Saint-Louis, 44 Boulevard Saint-Michel, 75006 Paris, France.
Phys Rev Lett. 2011 Mar 11;106(10):107203. doi: 10.1103/PhysRevLett.106.107203. Epub 2011 Mar 8.
We investigate the stability of the topological phase of the toric code model in the presence of a uniform magnetic field by means of variational and high-order series expansion approaches. We find that when this perturbation is strong enough, the system undergoes a topological phase transition whose first- or second-order nature depends on the field orientation. When this transition is of second order, it is in the Ising universality class except for a special line on which the critical exponent driving the closure of the gap varies continuously, unveiling a new topological universality class.
我们通过变分法和高阶级数展开方法研究了外加均匀磁场下 Toric 码模型拓扑相的稳定性。我们发现，当这个微扰足够强时，系统会经历拓扑相变，其阶数取决于磁场的方向。当这个相变是二阶相变时，它属于 Ising universality class，除了一条特殊的线，这条线上驱动能隙闭合的临界指数连续变化，揭示了一个新的拓扑普适类。
