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arXiv · 2512.15400

Ultrafast Strongly Anisotropic Valleytronics in SnSe

Yiming Pan·Sotirios Fragkos·Dominique Descamps·Stéphane Petit·Fabio Caruso·Samuel Beaulieu
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Abstract

Valleytronics aims to control electrons in a valley-specific manner for quantum information manipulation. Due to their strong in-plane anisotropy, which enables polarization-controlled optical transitions to distinct nondegenerate valleys, group-IV monochalcogenides have been recently proposed as promising candidates for next-generation valleytronic materials. However, ultrafast nonequilibrium dynamics following optical preparation of valley-polarized states remain completely unexplored in these systems. Combining time- and angle-resolved extreme-ultraviolet photoemission spectroscopy with time-dependent Boltzmann equation simulations, we investigate ultrafast valley polarization dynamics following polarization-controlled photoexcitation in SnSe. We show that selective excitation to valleys at global conduction minima yields nearly unity and time-independent valley polarization. In contrast, photoexcitation to the other valley channel leads to ultrafast decay and reversal of valley polarization on sub-picosecond timescales due to intervalley scattering mediated by strong electron-phonon coupling with an optical phonon mode. Our findings reveal strongly anisotropic and radically different nonequilibrium valley physics than in most common two-dimensional valleytronics materials.

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Yiming Pan, Sotirios Fragkos, Dominique Descamps, Stéphane Petit, Fabio Caruso, Samuel Beaulieu. 2025-12-17. Ultrafast Strongly Anisotropic Valleytronics in SnSe. https://arxiv.org/abs/2512.15400

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