Manipulating spins can enable the development of ultralow power electronics, but previous approaches were limited by the strength of the effective field and high-quality structures. Wang et al. explore a mechanism to manipulate spins at room temperature with monolayer tungsten diselenide, in virtue of a novel giant spin-orbit field.
The authors found their setup could achieve spin flipping at room temperature, which manifested as changes in the sign of measured magnetoresistance. By altering the number of tungsten diselenide layers in their setup, the team showed the magnetoresistance oscillated between positive and negative values. Through experiments and simulations, the authors identified valley-Zeeman spin-orbit coupling, which induces an out-of-plane effective field of about 650 Tesla, as the origin of this effect.
“For the first time, we have realized the control of spin currents by using the valley-Zeeman spin-orbit field of tungsten diselenide, which manifests as negative magnetoresistance in the case of monolayer tungsten diselenide,” author Xiaoyang Lin said. “This work uncovers a new mechanism of magnetoresistance effect unlike those previously found in vertical spin valves.”
To characterize the valley-Zeeman effect, the authors fabricated a tungsten diselenide spin valve using photolithography, electron-beam evaporation, and chemical vapor deposition, then determined electron transport through the device by measuring its resistance after applying a magnetic field. The authors also calculated the spin-resolved quantum transmission coefficients, whose non-zero value in different states indicated the possibility of spin-flipping and helped account for the team’s observed magnetoresistance effect.
Future work may include investigating how the spin-orbit field of tungsten diselenide can be controlled using a gate voltage.
Source: “Spin manipulation by giant valley-Zeeman spin-orbit field in atom-thick WSe2,” by Xinhe Wang, Wei Yang, Wang Yang, Yuan Cao, Xiaoyang Lin, Guodong Wei, Haichang Lu, Peizhe Tang, and Weisheng Zhao, Applied Physics Reviews (2022). The article can be accessed at https://doi.org/10.1063/5.0089162.