1.
Phys Rev Lett
; 106(10): 107203, 2011 Mar 11.
Article
in English
| MEDLINE
| ID: mdl-21469828
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.