Enhanced Valley Polarization via Nonlinear Cascaded Quantum-Geometric Selection Rules
Abstract
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.
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BibTeX
@misc{courtade2026enhanced,
title = {{Enhanced Valley Polarization via Nonlinear Cascaded Quantum-Geometric Selection Rules}},
author = {Quentin Courtade and Sotirios Fragkos and Dominique Descamps and Stéphane Petit and Yann Mairesse and Michael Schüler and Samuel Beaulieu},
howpublished = {HAL},
year = {2026},
month = nov,
doi = {10.48550/arxiv.2605.03663},
url = {https://hal.science/hal-05778004v1},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Enhanced Valley Polarization via Nonlinear Cascaded Quantum-Geometric Selection Rules
AU - Quentin Courtade
AU - Sotirios Fragkos
AU - Dominique Descamps
AU - Stéphane Petit
AU - Yann Mairesse
AU - Michael Schüler
AU - Samuel Beaulieu
PY - 2026
DA - 2026/11/05
PB - HAL
DO - 10.48550/arxiv.2605.03663
UR - https://hal.science/hal-05778004v1
AB - 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.
ER -