Strain-enhanced optical absorbance of topological insulator films

Mathias Rosdahl Brems, Jens Paaske, Anders Mathias Lunde, Morten Willatzen

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Abstract

Topological insulator films are promising materials for optoelectronics due to a strong optical absorption and a thickness-dependent band gap of the topological surface states. They are superior candidates for photodetector applications in the THz-infrared spectrum, with a potential performance higher than graphene. Using a firstprinciples k.p Hamiltonian, incorporating all symmetry-allowed terms to second order in the wave vector k, first order in the strain c, and of order ck, we demonstrate a significantly improved optoelectronic performance due to strain. For Bi2Se3 films of variable thickness, the surface-state band gap, and thereby the optical absorption, can be effectively tuned by the application of uniaxial strain epsilon(zz), leading to a divergent band-edge absorbance for epsilon(zz) greater than or similar to 6%. Shear strain breaks the crystal symmetry and leads to an absorbance varying significantly with polarization direction. Remarkably, the directional average of the absorbance always increases with strain, independent of material parameters.
Original languageEnglish
Article number081402
JournalPhysical Review B
Volume97
Issue number8
Number of pages5
ISSN1098-0121
DOIs
Publication statusPublished - 2018

Keywords

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Microwave, radiofrequency and terahertz wave interactions with condensed matter
  • Optical constants and parameters (condensed matter)
  • Infrared and Raman spectra in inorganic crystals
  • Optical properties of other inorganic semiconductors and insulators (thin films, low-dimensional and nanoscale structures)

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