Stress-induced bandgap renormalization in atomic crystals

Single atomic layers of two-dimensional (2D) transition metal dichalcogenides (TMDs) are promising candidates for integration of optical and electronic circuits due to their extraordinary optical oscillator strength and large exciton binding energy. Customizing the exciton energy of the TMDs is a direct way to control the light-matter interaction. Here we demonstrate that the electronic band gap of tungsten diselenide WSe₂ can be tuned continuously with the application of the uniaxial tensile strain. The energy is redshifted with a rate of ∼62.5 meV/% strain for exciton A, determined by photoluminescence spectroscopy along with Finite Element Method modeling using the commercial software ANSYS. The uniaxial bandgap deformation potential (DP) of the electronic bandgap of monolayer WSe₂ can be computed directly from our measurements and is about −6.3 ± 0.5 eV. Our results agree well with first-principles calculations. The ability to control the renormalization of the bandgap in 2D materials with strain could be used in flexible electronics or optoelectronic devices such as a TMDs based microcavity.