New Pathway to Valleytronics
Pump-induced change of probe beam reflectivity. Illustrates optical Stark shifts of exciton transitions induced by pump pulses.
Demonstrated that a well-established phenomenon known as the ‘optical Stark effect’ can be used to selectively control photoexcited electron/hole pairs (excitons) in different energy valleys as electrons move, wavelike, through a 2D semiconductor.
Significance and Impact
Understanding how to control excitons in different energy valleys opens the possibility of ultrafast manipulation for quantum information applications, with information coded based on electrons’ wavelike movement.
- In valleytronics, electrons move through a 2D semiconductor as a wave with two energy valleys, each characterized by a quantum valley number that encodes information
- Scientists generated ultrafast and ultrahigh pseudomagnetic fields using circularly polarized femtosecond light pulses to selectively control the valley degree of freedom
- Ultrafast pump-probe spectroscopy was used to observe a pure and valley-selective optical Stark effect
- The optical Stark effect describes an energy shift in a two-level system induced by a non-resonant laser field