De-Eknamkul C, Huang W, Zhang X, Ren Y, Cubukcu E. Transport and Spatial Separation of Valley Coherence via Few Layer WS
2 Exciton-Polaritons.
ACS Photonics 2024;
11:1078-1084. [PMID:
38576862 PMCID:
PMC10993736 DOI:
10.1021/acsphotonics.3c01484]
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Abstract
The optical response in two-dimensional transition-metal dichalcogenides (2D TMDCs) is dominated by excitons. The lack of spatial inversion symmetry in the hexagonal lattice within each TMDC layer leads to valley-dependent excitonic emission of photoluminescence. Here, we demonstrate experimentally the spatial separation of valley coherent emission into orthogonal directions through self-resonant exciton polaritons of a free-standing three-layer (3L) WS2 waveguide. This was achieved by patterning a photonic crystal consisting of a square array of holes allowing for the far field probing of valley coherence of engendered exciton-polaritons. Furthermore, we report detailed experimental modal characterization of this coupled system in good agreement with theory. Momentum space measurements reveal a degree of valley coherence in the range 30-60%. This work provides a platform for manipulation of valley excitons in coherent light-matter states for potential implementations of valley-coherent optoelectronics.
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