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Paper   IPM / P / 13708
School of Physics
  Title:   Optical responses and optical activity of ultrathin film topological insulator
1.  F. Parhizgar
2.  A. G. Moghaddam
3.  R. Asgari
  Status:   Published
  Journal: Phys. Rev. B
  Vol.:  92
  Year:  2015
  Pages:   045429
  Supported by:  IPM
We investigate the optical properties of an ultrathin film of a topological insulator at the presence of an in-plane magnetic field. We show that due to the combination of overlap between the surface states of the two layers and the magnetic field, the optical conductivity can show strong anisotropy. This leads to the effective optical activity of the ultrathin film by influencing the circularly polarized incident light. Intriguingly, for a range of magnetic fields, the reflected and transmitted lights exhibit elliptic character. Even for certain values almost linear polarizations are obtained, indicating that the thin film can act as a polaroid in reflection. All these features are discussed in the context of the time reversal symmetry breaking as one of key ingredients for the optical activity.

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