Nanowerk April 23, 2023
Electrons in two-dimensional materials possess an additional quantum attribute, the valley pseudospin, labeled as K and K’—analogous to the spin up and spin down. Most of the research to achieve valley-selective excitations in valleytronics depends on resonant circularly polarized light with a given helicity. Not only acquiring valley-selective electron excitation but also switching the excitation from one valley to another is quintessential for bringing valleytronics-based technologies to reality. Researchers in India introduced a coherent control protocol to initiate valley-selective excitation, de-excitation, and switch the excitation from one valley to another on the fly within tens of femtoseconds. They tested the protocol in monolayer graphene and molybdenum disulfide. According to the researchers the protocol is equally applicable to both gapped and gapless two-dimensional materials, it is robust, insensitive to significant parameters of the protocol, such as dephasing times, wavelengths, and time delays of the laser pulses and opens an alternative realm of valley switch at petahertz rate… read more. TECHNICAL ARTICLE
Schematic of an all-optical ultrafast valley switch in a two-dimensional material… Credit: Phys. Rev. Applied 19, 34056 – 17 March 2023