A study has shown that the optical Stark effect, which describes the energy shift in a two-level system induced by a non-resonant laser field, can be used to control valley excitons in MX2 semiconductors.
A potential avenue to quantum computing currently generating quite the buzz in the high-tech industry is "valleytronics," in which information is coded based on the wavelike motion of electrons moving through certain two-dimensional (2D) semiconductors. Now, a promising new pathway to valleytronic technology has been uncovered by researchers with the Lawrence Berkeley National Laboratory (Berkeley Lab). Feng Wang, a condensed matter physicist with Berkeley Lab's Materials Sciences Division, led a study in which it was demonstrated that a well-established phenomenon known as the "optical Stark effect" can be used to selectively control photoexcited electrons/hole pairs - referred to as excitons -in different energy valleys. In valleytronics, electrons move through the lattice of a 2D semiconductor as a wave with two energy valleys, each valley being characterized by a distinct momentum and quantum valley number. This quantum valley number can be used to encode information when the electrons are in a minimum energy valley. The technique is analogous to spintronics, in which information is encoded in a quantum spin number. "This is the first demonstration of the important role the optical Stark effect can play in valleytronics," Feng says.
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