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SYHS: Symposium Physics of van der Waals 2D Heterostructures

SYHS 1: Physics of van der Waals 2D Heterostructures

SYHS 1.4: Invited Talk

Friday, March 31, 2023, 11:15–11:45, HSZ 01

Spin-orbit proximity in van der Waals heterostructures — •Felix Casanova — CIC nanoGUNE, Donostia, Basque Country

Transition metal dichalcogenides (TMD) can be used to enhance the spin-orbit coupling of graphene, leading to new spin transport channels with unprecedented spin textures [1]. We have optimized bilayer graphene/WSe₂ van der Waals heterostructures to achieve magnetic-field-free spin precession. Remarkably, the sign of the precessing spin polarization can be tuned electrically by backgate voltage and drift current [2], being the first realization of a spin field-effect transistor at room temperature in a diffusive system, a long-awaited goal.

The spin-orbit proximity in graphene/TMD van der Waals heterostructures also leads to spin-to-charge conversion (SCC) of spins along z due to spin Hall effect (SHE), which was first observed by our group using MoS₂ as the TMD [3]. The combination of long-distance spin transport and SHE in the same material gives rise to an unprecedented figure of merit (product of spin Hall angle and spin diffusion length) of 40 nm in graphene proximitized with WSe₂, which is also gate tunable [4]. Finally, we demonstrate SCC of spins oriented in all three directions (x, y, and z) in graphene/NbSe₂ heterostructure, due to spin-orbit proximity and broken symmetry at the twisted graphene/NbSe₂ interface [5].
[1] Gmitra and Fabian, Phys. Rev. B 93, 155104 (2016)
[2] Ingla-Aynés et al., Phys. Rev. Lett. 127, 047202 (2021)
[3] Safeer et al., Nano Lett. 19, 1074 (2019)
[4] Herling et al., APL Mater. 8, 071103 (2020)
[5] Ingla-Aynés et al., 2D Mater. 9, 045001 (2022)