Enhanced Valley Polarization via Nonlinear Cascaded Quantum-Geometric Selection Rules
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arXiv
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| Format: | Preprint |
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2026
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| author | Courtade, Quentin Fragkos, Sotirios Descamps, Dominique Petit, Stéphane Mairesse, Yann Schüler, Michael Beaulieu, Samuel |
| author_facet | Courtade, Quentin Fragkos, Sotirios Descamps, Dominique Petit, Stéphane Mairesse, Yann Schüler, Michael Beaulieu, Samuel |
| contents | The quantum geometric properties of Bloch electrons fundamentally govern light-matter interactions and optical selection rules in solids. In semiconducting transition-metal dichalcogenides, circularly polarized excitation near the band edge enables valley-selective interband transitions, providing the basis for valleytronics. While nonlinear optical protocols are being developed to manipulate and probe valley selection rules, they largely rely on band-edge transitions that proceed via virtual intermediate states. Here, we demonstrate a doubly resonant cascaded nonlinear pathway from the valence band to high-lying states, mediated by a real intermediate state whose participation substantially reshapes the valley optical selection rules. Using time- and angle-resolved extreme-ultraviolet photoemission spectroscopy in combination with a time-dependent Lindblad master-equation formalism, we show that this cascaded nonlinear photoexcitation produces a substantially enhanced high-lying valley polarization compared to the conventional linear optical response near the band edge. The extension of the quantum-geometry-based selection rules to the nonlinear regime and high-lying bands offers new perspectives for ultrafast valleytronics and should play a determinant role in strong-field-driven phenomena in quantum materials. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2605_03663 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Enhanced Valley Polarization via Nonlinear Cascaded Quantum-Geometric Selection Rules Courtade, Quentin Fragkos, Sotirios Descamps, Dominique Petit, Stéphane Mairesse, Yann Schüler, Michael Beaulieu, Samuel Materials Science The quantum geometric properties of Bloch electrons fundamentally govern light-matter interactions and optical selection rules in solids. In semiconducting transition-metal dichalcogenides, circularly polarized excitation near the band edge enables valley-selective interband transitions, providing the basis for valleytronics. While nonlinear optical protocols are being developed to manipulate and probe valley selection rules, they largely rely on band-edge transitions that proceed via virtual intermediate states. Here, we demonstrate a doubly resonant cascaded nonlinear pathway from the valence band to high-lying states, mediated by a real intermediate state whose participation substantially reshapes the valley optical selection rules. Using time- and angle-resolved extreme-ultraviolet photoemission spectroscopy in combination with a time-dependent Lindblad master-equation formalism, we show that this cascaded nonlinear photoexcitation produces a substantially enhanced high-lying valley polarization compared to the conventional linear optical response near the band edge. The extension of the quantum-geometry-based selection rules to the nonlinear regime and high-lying bands offers new perspectives for ultrafast valleytronics and should play a determinant role in strong-field-driven phenomena in quantum materials. |
| title | Enhanced Valley Polarization via Nonlinear Cascaded Quantum-Geometric Selection Rules |
| topic | Materials Science |
| url | https://arxiv.org/abs/2605.03663 |