Enhancing Resonant Second-Harmonic Generation in Bilayer WSe<sub>2</sub> by Layer-Dependent Exciton-Polaron Effect.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 39528357.
- Also identified by DOI 10.1021/acs.nanolett.4c04544 and PMC identifier 11583334.
- Licence recorded as CC BY-NC-ND.
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Abstract
Two-dimensional (2D) materials serve as exceptional platforms for controlled second-harmonic generation (SHG). Current approaches to SHG control often depend on nonresonant conditions or symmetry breaking via single-gate control. Here, we employ dual-gate bilayer WSe<sub>2</sub> to demonstrate an SHG enhancement concept that leverages strong exciton resonance and a layer-dependent exciton-polaron effect. By selectively localizing injected holes within one layer, we induce exciton-polaron states in the hole-filled layer while maintaining normal exciton states in the charge-neutral layer. The distinct resonant conditions of these layers effectively break interlayer inversion symmetry, thereby promoting resonant SHG. This method achieves a remarkable 40-fold enhancement of SHG at minimal electric field, equivalent to conditions near the dielectric-breakdown threshold but using only ∼3% of the critical breakdown field. Our results highlight SHG sensitivity to carrier density and type, offering a new tool for manipulating SHG and probing quantum states in 2D excitonic systems.