Lightwave Valleytronics at Multi-Terahertz Clock Rates

As conventional electronic is approaching its fundamental limits, huge efforts have been taken to explore new concepts of ultrafast control at the quantum level. Lightwave electronics — the foundation of attosecond science [1] — has opened a spectacular perspective by utilizing the carrier wave of an intense light pulse to steer the translational motion of charges faster than a single cycle of light [1–4]. Despite their promising potential as future information carrier, the electron's internal quantum attributes such as the spin and the valley pseudospin [5] have not been switchable at optical clock rates.