Researchers at CIC nanoGUNE BRTA, Charles University in Prague and IKERBASQUE have designed a new complex material with unique properties that could be beneficial for spintronics.
Twist engineering has emerged as a fascinating approach for modulating electronic properties in van der Waals heterostructures. While theoretical works have predicted the modulation of spin texture in graphene-based heterostructures by twist angle, experimental studies are lacking. In this recent work, by performing spin precession experiments, the team demonstrates tunability of the spin texture and associated spin–charge interconversion with twist angle in WSe2/graphene heterostructures.
For specific twist angles, the scientists detected a spin component radial with the electron’s momentum, in addition to the standard orthogonal component.
“In this work we studied the stacking of two layers of graphene and tungsten selenide (WSe2),” explained Ikerbasque Research Professor Félix Casanova, co-leader of the Nanodevices group at nanoGUNE and who led this work. “If the two layers are placed one on top of the other and rotated at a precise angle, a spin current is generated in a desired specific direction,” added Félix Casanova.
Spin is normally transferred in a direction perpendicular to the electric current. Handling these spin currents is one of the main limitations of spintronics – electronics that uses spin to store, handle and transfer information. However, “this work shows that this limitation in fact disappears when suitable materials are used,” stressed Félix Casanova.
Casanova concluded that “by simply stacking two layers and applying a ‘magic’ twist, new spin-related properties that do not exist in the initial materials can be obtained”. “The more flexibility we have in the choice of materials, the greater the design possibilities are for next-generation devices.”
Their results show that the helicity of the spin texture can be reversed by twist angle, highlighting the critical role of the twist angle in the spin–orbit properties of WSe2/graphene heterostructures and paving the way for the development of spin-twistronic devices.