Quantum interference and occupation control in high harmonic generation from monolayer WS2

Minjeong Kim; Taeho Kim; Anna Galler; Dasol Kim; Alexis Chacon; Xiangxin Gong; Yuhui Yang; Rouli Fang; Kenji Watanabe; Takashi Taniguchi; B. J. Kim; Sang Hoon Chae; Moon-Ho Jo; Angel Rubio; Ofer Neufeld; Jonghwan Kim

doi:10.1038/s41467-025-65725-9

Journal article Quantum interference and occupation control in high harmonic generation from monolayer WS2

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Minjeong Kim, Taeho Kim, Anna Galler, Dasol Kim, Alexis Chacon, Xiangxin Gong, Yuhui Yang, Rouli Fang, Kenji Watanabe, Takashi Taniguchi, B. J. Kim, Sang Hoon Chae, Moon-Ho Jo, Angel Rubio, Ofer Neufeld, Jonghwan Kim. Quantum interference and occupation control in high harmonic generation from monolayer WS2. Nature Communications. 2025, 16 (), 9825. https://doi.org/10.1038/s41467-025-65725-9

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Two-dimensional hexagonal materials such as transition metal dichalcogenides exhibit valley degrees of freedom, offering fascinating potential for valley-based quantum computing and optoelectronics. In nonlinear optics, the K and K’ valleys provide excitation resonances that can be used for ultrafast control of excitons, Bloch oscillations, and Floquet physics. Under intense laser fields, however, the role of coherent carrier dynamics away from the K/K’ valleys is largely unexplored. In this study, we observe quantum interferences in high harmonic generation from monolayer WS2 as laser fields drive electrons from the valleys across the full Brillouin zone. In the perturbative regime, interband resonances at the valleys enhance high harmonic generation through multi- photon excitations. In the strong-field regime, the high harmonic spectrum is sensitively controlled by light-driven quantum interferences between the interband valley resonances and intraband currents originating from electrons occupying various points in the Brillouin zone, also away from K/K’ valleys such as 𝚪 and M. Our experimental observations are in strong agreement with quantum simulations, validating their interpretation. This work proposes new routes for harnessing laser-driven quantum interference in two-dimensional hexagonal systems and all-optical techniques to occupy and read-out electronic structures in the full Brillouin zone via strong-field nonlinear optics, advancing quantum technologies.

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