Mechanical Detuning of Exciton-Phonon Resonance in WS2

Abstract

Controlling resonant Raman scattering in two-dimensional semiconductors typically requires tuning the excitation energy to match excitonic transitions. Here we show that mechanical deformation can achieve the same effect without changing the laser energy, enabling a controlled transition between resonant and non-resonant Raman scattering at fixed excitation. By applying biaxial strain up to 1.3% to WS2, the B exciton is red-shifted by 180 meV. This large excitonic shift leads to a pronounced collapse of the double-resonant 2LA(M) mode under 532 nm excitation, quantitatively described by a resonance model formulated in terms of the B exciton energy. Meanwhile, first-order phonons remain narrow and reversible, confirming elastic deformation and efficient strain transfer. These results establish mechanical strain as an effective knob to control exciton-phonon mediated light-matter interactions. They enable deterministic and reversible tuning of resonance-enhanced Raman scattering and excitonic optical responses in layered semiconductors.

27 pages, 5 figures

References in corpus (7)

• Uniaxial Strain in Graphene by Raman Spectroscopy: G peak splitting, Gruneisen Parameters and Sample Orientation
• Helicity resolved Raman scattering of MoS2, MoSe2, WS2 and WSe2 atomic layers
• Strain control of hybridization between dark and localized excitons in a 2D semiconductor
• Biaxial versus uniaxial strain tuning of single-layer MoS${}_2$
• Biaxial Tensile Strain Enhances Electron Mobility of Monolayer Transition Metal Dichalcogenides
• Large trion binding energy in monolayer WS${}_2$ via strain-enhanced electron-phonon coupling
• Biaxial strain tuning of exciton energy and polarization in monolayer WS2