Quantum phase transition and fractional excitations in a topological insulator thin film with Zeeman and excitonic masses

Abstract

We study the zero-temperature phase diagram and fractional excitation when a thin film of 3D topological insulator has two competing masses: T- symmetric exciton condensation and T- breaking Zeeman effect. Two topologically distinct phases are identified: in one, the quasiparticles can be viewed as in a quantum spin Hall phase, and in the other a quantum anomalous Hall phase. The vortices of the exciton order parameter can carry fractional charge and statistics of electrons in both phases. When the system undergoes the quantum phase transition between these two phases, the charges, statistics and the number of fermionic zero mode of the excitonic vortices are also changed. We derive the effective field theory for vortices and external gauge field by directly integrating out fermions and present an explicit wave function for the fermionic zero mode localized at the excitonic vortices with or without orbital magnetic field. The quantum phase transition can be measured by optical Faraday or Kerr effect experiments, and in closing we discuss the conditions required to create the excitonic condensate.

8 pages, 3 figures, accepted version, editorial suggestion

References in corpus (8)

• Superconducting proximity effect and Majorana fermions at the surface of a topological insulator
• Topological Field Theory of Time-Reversal Invariant Insulators
• Three dimensional topological invariants for time reversal invariant Hamiltonians and the three dimensional quantum spin Hall effect
• Electron fractionalization in two-dimensional graphenelike structures
• Room-Temperature Superfluidity in Graphene Bilayers
• Exciton condensation and charge fractionalization in a topological insulator film
• Electron screening and excitonic condensation in double-layer graphene systems
• Vortices, zero modes and fractionalization in bilayer-graphene exciton condensate

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• Reentrant topological phases in Mn-doped HgTe quantum wells
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