title: Robustness of a perturbed topological phase.
abstract: 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.
authors.affiliation: Lycée Saint-Louis, 44 Boulevard Saint-Michel, 75006 Paris, France.
authors.forename: Sébastien
authors.initials: S
authors.lastname: Dusuel
authors.forename: Michael
authors.initials: M
authors.lastname: Kamfor
authors.forename: Román
authors.initials: R
authors.lastname: Orús
authors.forename: Kai Phillip
authors.initials: KP
authors.lastname: Schmidt
authors.forename: Julien
authors.initials: J
authors.lastname: Vidal