On-line SPICE-SPIN+X Seminars

On-line Seminar: 05.02.2025 - 15:00 CET

Spintronics with van der Waals heterostructures

Sergio Valenzuela, ICREA and ICN2


Van der Waals (vdW) heterostructures provide a versatile platform for investigating spintronic phenomena, particularly through their atomically sharp interfaces and tunable properties [1,2]. Such heterostructures allow for the design of proximity effects via short-range interactions, enabling the exploration of spin-orbit coupling and spin-dependent transport in ways not easily achieved with conventional materials [1].
In this talk, I will begin by addressing the importance of boundary states and the quality of the topological insulator (TI)/ferromagnet (FM) interface in maximising spin-orbit torques (SOT). For example, vdW TIs such as (Bi,Sb)2Te3 can influence spin transport and charge-to-spin conversion processes due to spin-momentum locking. I will show how introducing a non-magnetic metallic [3] or, in particular, graphene [4] interlayer between the TI and FM, when the FM is a transition metal, significantly modifies the nature and enhances the efficiency of SOTs [3,4]. Similar enhancements observed with sharp interfaces between TIs and vdW FMs [5] further illustrate the potential of interfacial engineering in shaping spintronic functionalities.
Building on these examples, I will then discuss how proximity effects in graphene can be identified through spin transport dynamics, focusing on our findings on spin relaxation anisotropy [6] and charge-to-spin interconversion [7,8]. I will highlight the role of crystal symmetry, showing how systems with reduced symmetry give rise to diverse spin-orbit fields and unconventional charge-to-spin conversion components, alongside methods for determining their underlying mechanisms. Furthermore, I will demonstrate that electrostatic gating can tune spin relaxation anisotropy, as well as spin Hall and spin galvanic effects, with these phenomena remaining robust up to room temperature [6-8].

[1] J. F. Sierra et al., Nature Nano. 16, 856–868 (2021)
[2] H. Yang, S. O. Valenzuela et al., Nature 606, 663 (2022)
[3] F. Bonell et al., Nano Lett. 20, 5893 (2020)
[4] R. Galceran et al., Adv. Mater. Interfaces 9, 2201997 (2022): T. Guillet, V. Zatko et al., unpublished (2025)
[5] T. Guillet et al., Nano Lett. 24, 822 (2024)
[6] B. Raes et al. Nature Commun. 7, 11444 (2016); L. A. Benítez et al., Nature Phys. 14 (2018); APL Materials 7, 120701 (2019); J. F. Sierra, J. Světlík et al., Nature Mater. (in press 02/2025)
[7] L. A. Benítez et al., Nature Mater. 19, 170 (2020)
[8] L. Camosi et al., 2D Mater. 9, 035014 (2022)

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