Biaxial strain tuning of exciton energy and polarization in monolayer WS2

TL;DR

This study investigates how biaxial tensile strain affects the optical properties of WS2 monolayers, revealing significant exciton energy shifts and polarization changes, which are crucial for strain-engineered optoelectronic applications.

Contribution

The paper provides experimental insights into the effects of biaxial strain on exciton energy and polarization in WS2 monolayers, including separating strain-induced energy detuning from pure strain effects.

Findings

Exciton emission shifts by approximately -130 meV per % strain.

Circular polarization degree decreases monotonically with applied strain.

Strain influences exciton oscillator strength and polarization relaxation channels.

Abstract

We perform micro-photoluminescence and Raman experiments to examine the impact of biaxial tensile strain on the optical properties of WS2 monolayers. A strong shift on the order of -130 meV per % of strain is observed in the neutral exciton emission at room temperature. Under near-resonant excitation we measure a monotonic decrease in the circular polarization degree under applied strain. We experimentally separate the effect of the strain-induced energy detuning and evaluate the pure effect coming from biaxial strain. The analysis shows that the suppression of the circular polarization degree under biaxial strain is related to an interplay of energy and polarization relaxation channels as well as to variations in the exciton oscillator strength affecting the long-range exchange interaction.