Article,
Conformality loss and quantum criticality in topological Higgs electrodynamics in 2+1 dimensions
Phys. Rev. D, 100 (8): 085005 (Oct 15, 2019)
DOI: 10.1103/PhysRevD.100.085005
Abstract
The electromagnetic response of topological insulators and
superconductors is governed by a modified set of Maxwell equations that
derive from a topological Chern-Simons (CS) term in the effective
Lagrangian with coupling constant kappa. Here, we consider a topological
superconductor or, equivalently, an Abelian Higgs model in 2 + 1
dimensions with a global O(2N) symmetry in the presence of a CS term,
but without a Maxwell term. At large kappa, the gauge field decouples
from the complex scalar field, leading to a quantum critical behavior in
the O(2N) universality class. When the Higgs field is massive, the
universality class is still governed by the O(2N) fixed point. However,
we show that the massless theory belongs to a completely different
universality class, exhibiting an exotic critical behavior beyond the
Landau-Ginzburg-Wilson paradigm. For finite kappa above a certain
critical value kappa(c), a quantum critical behavior with continuously
varying critical exponents arises. However, as a function kappa, a
transition takes place for vertical bar kappa vertical bar < kappa(c)
where conformality is lost. Strongly modified scaling relations ensue.
For instance, in the case where kappa(2) > kappa(2)(c), leading to the
existence of a conformal fixed point, critical exponents are a function
of kappa.
