Strain tuning of optical properties in Bi2Se3

Based on symmetry principles we determine the most general Hamiltonian for the low energy physics of Bi
₂
Se
₃
, including contributions due to a static electric field and strain. The full three-dimensional model is projected into the surface states at k
_∥
= 0, giving an effective two-dimensional Hamiltonian for the surface states. Contributions from the strain tensor breaks the anisotropy of the surface state spectrum, giving an elleptical Dirac cone. Within this model we calculate the absorption spectrum for an ultra-thin film. We show that the fundamental absorption edge can be effectively tuned by application of uniaxial strain.