Phys.org April 13, 2023
Spin and valley indices represent the key quantum labels of quasi-particles in a wide class of two-dimensional materials and form the foundational elements of the fields of spintronics and valleytronics. Researchers in Germany have discovered a route to induce and control the flow of spin and valley currents at ultrafast times with specially designed laser pulses, offering a new perspective on the ongoing search for the next generation of information technologies. They showed that femtosecond laser light combining optical frequency circularly polarized pulse and a terahertz (THz) frequency linearly polarized pulse can generate precisely tailored and 90% pure spin currents for the dichalcogenide WSe2 and >75% pure valley currents for bilayer graphene with gaps greater than 120 millielectron volts. The frequency of the circular light component and the polarization vector of the THz light component were shown to represent the key control parameters of these pulses. According to the researchers their results open a route toward light control over spin/valley current states at ultrafast times… read more. Open Access TECHNICAL ARTICLEÂ
lllustration of exciton splitting in the organic semiconductor pentacene… Credit: TU Berlin