| We investigate the stability of the topological phase in the toric code model in the presence of an arbitrary uniform magnetic field by means of variational approach (iPEPS) and high order series expansion (PCUT). It is found that when this perturbation is strong enough, the anyonic gap closes and the system undergoes a phase transition whose 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. |
|