Strain-enhanced optical absorbance of topological insulator films

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 first-principles $k\cdot p$ Hamiltonian, incorporating all symmetry-allowed terms to second order in the wave vector $k$, first order in the strain $\epsilon$ and of order $\epsilon k$, we demonstrate significantly improved optoelectronic performance due to strain. For Bi${}_2$Se${}_3$ films of variable thickness, the surface state band gap, and thereby the optical absorption, can be effectively tuned by application of uniaxial strain, ${\epsilon }_{zz}$, leading to a divergent band edge absorbance for ${\epsilon }_{zz}\gtrsim 6\%$. 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.

References in corpus (9)

• Discovery (theoretical prediction and experimental observation) of a large-gap topological-insulator class with spin-polarized single-Dirac-cone on the surface
• Crossover of Three-Dimensional Topological Insulator of Bi2Se3 to the Two-Dimensional Limit
• Model Hamiltonian for Topological Insulators
• Effective continuous model for surface states and thin films of three dimensional topological insulators
• Topological insulators for high performance terahertz to infrared applications
• Strong nonlinear terahertz response induced by Dirac surface states in Bi2Se3 Topological Insulator
• First Principles Investigations of the Atomic, Electronic, and Thermoelectric Properties of Equilibrium and Strained Bi2Se3 & Bi2Te3, with van der Waals Interactions
• Theoretical investigation of the evolution of the topological phase of Bi${}_2$Se${}_3$ under mechanical strain
• Calculation of divergent photon absorption in ultrathin films of a topological insulator

Cited by in corpus (3)

• Topological properties of multi-terminal superconducting nanostructures: effect of a continuous spectrum
• Symmetry analysis of strain, electric and magnetic fields in the ${\text{Bi}}_2{\text{Se}}_3$-class of topological insulators
• Weyl point immersed in a continuous spectrum: an example from superconducting nanostructures