2025/08/10 by Kim, Youngjae
#FOS: Physical sciences #Materials Science (cond-mat.mtrl-sci) #Optics (physics.optics) #Strongly Correlated Electrons (cond-mat.str-el)
paper · doi:10.48550/arxiv.2508.07213
The selective control of specific momentum valleys lies at the core of valleytronics, a field that has thus far focused primarily on the K and K' valleys in transition metal dichalcogenides (TMDs). However, direct optical access to other low-lying yet conventionally inaccessible valleys such as the sixfold degenerate Q valleys has remained an outstanding challenge, fundamentally limiting the exploitation of the full valley degree of freedom for information processing. Here, we theoretically introduce an emergent light-wave valley selection rule that enables deterministic and high fidelity excitation of any single Q valley in monolayer TMDs. By coherently combining a circularly polarized pump pulse with a linearly polarized driver pulse, we engineer distinct quantum pathways that unambiguously excited electrons into a targeted Q valley, completely decoupled from the conventional K/K' valleys. This all-optical scheme achieves near-unity (∼100%) valley polarization across an exceptionally broad ultrafast window, from the terahertz (1012~Hz) to petahertz (1015~Hz) regimes, enabling single Q valley polarization on femtosecond timescales. Our findings establish a new paradigm of light-wave quantum metrology in valleytronics, unlocking the Q-valley subspace for scalable multi-state valley information processing.