Speaker
Description
Spin-orbit torque (SOT) in van der Waals heterostructures offers a pathway to energy-efficient spintronic devices. The proximity of a transition-metal dichalcogenide to graphene can have a profound effect on the induced magnetism and spin texture of graphene. One of the promising materials for SOT research is 1T-TaS$_2$. A monolayer of 1T-TaS$_2$ comprises strong spin-orbit coupling, charge density wave correlated phase with a David star pattern, and spontaneous in-plane magnetization. When a layer of graphene is placed on 1T-TaS$_2$ monolayer, a spin-orbit coupling and exchange interaction is proximitized to the graphene electronic structure. This enables the generation of self-induced torque on graphene electrons when a charge current passes through the graphene.
Using a tight-binding model with parameters fitted to density functional theory data, combined with quantum transport simulations, we compute spin-orbit torques for a range of Fermi levels to simulate electron and hole doping. We quantify the contributions to the self-torque originating from exchange interaction, intrinsic spin-orbit coupling, and Rashba spin-orbit coupling. Our results reveal that the stacking configuration of graphene on 1T-TaS$_2$ plays a critical role in the strength of the spin-orbit torque. Specifically, when graphene is aligned in a top stacking configuration where a carbon atom is placed over the Ta atom of the David star center, the torque values are significantly larger, by nearly an order of magnitude, compared to the hollow case where the center of the graphene ring and the David star are placed on top of each other. These findings not only deepen our understanding of SOT mechanisms in graphene/1T-TaS$_2$ heterostructures but also offer valuable insights for the design and optimization of spintronic devices based on such systems.
Acknowledgements
Funded by the European Union’s NextGenerationEU program through the Recovery and Resilience Plan for Slovakia under the Project No. 09I03-03-V04-00318.
