Seminarium Fizyki Ciała Stałego

Graphene-based van der Waals (vdW) heterostructures provide a versatile platform for engineeringspin–orbit coupling, exchange interactions, and symmetry breaking via proximity effects, whilepreserving graphene’s exceptional electronic quality [1,2]. In this seminar, I will present recenttheoretical advances in spin-dependent transport and topological phenomena in proximitized graphene,with particular emphasis on graphene deposited on transition-metal dichalcogenides (TMDs) andmagnetic transition-metal halides (TMHs).Building on our recent first-principles and effective-model studies of graphene-based vdW structures,we demonstrated that electrostatic gating, twist angle, and strain can position the graphene Dirac conesinside the band gap of adjacent insulating two-dimensional crystals (e.g., CrI₃, CrBr₃, MoS₂, and WSe₂),thereby enabling a controllable proximity regime. In this regime, the interplay of exchange andsymmetry-allowed spin–orbit fields gives rise to a variety of topological and valley-contrastingbehavior and supports efficient spin-to-charge conversion [2-5]. The derived low-energy effectiveHamiltonians accurately describe proximitized graphene and enable a detailed analysis of spindependent transport and Berry-curvature effects.I will discuss graphene deposited on semiconducting TMDs [4,5] and other ‘ex-so-tic’ vdWheterostructures [6,7], showing how spin-to-charge conversion efficiency and valley responses can betailored via twisting and electrostatic control. Within linear-response theory, one can identify regimeswhere the current-induced spin polarization, as well as the anomalous and spin Hall effects are stronglyenhanced, and we demonstrate that the valley Hall conductivity can approach quantized values in certainparameter ranges. I will also address the emergence of proximity-induced topological phases ingraphene–TMHs heterostructures, including conditions for realising Chern-insulator behavior and itsevolution under twist, gating, and strain [3,8-10]. Finally, I outline selected concepts for spin–orbittorque devices based on vdW heterostructures [11-14]. [1] K. Zollner, J. Fabian, 2D Materials 12, 013004 (2025) [2] A. Dyrdał, J. Barnaś, 2D Materials 4, 034003 (2017) [3] M. Jafari, M. Gmitra, A. Dyrdał, 2D Materials 13, 025008 (2026) [4] I. Wojciechowska, A. Dyrdał, Sci. Rep. 15, 39156 (2025) [5] K. Zollner, et al., Phys. Rev. B 108 (23), 235166 (2023) [6] K. Zollner, M. Gmitra, J. Fabian, Phys. Rev. Letters 125, 196402 (2020) [7] I. Wojciechowska, A. Dyrdał, Sci. Rep. 14, 23808 (2024); [8] J. Zhang, B. Zhao, T. Zhou, et al., Phys. Rev. B, 085401 (2018) [9] H. Zhang, et al., PCCP 21, 17087 (2019)[10] J.-T. Ren, Y. Feng, S.-S. Ke, et al., Adv. Physics Res. 4, 2300026 (2025)[11] A. Dyrdal, J. Barnaś, Phys Rev. B 92, 165404 (2015)[12] K. Zollner, M. D. Petrović, K. Dolui, et al., Phys. Rev. Research 2, 043057 (2020)[13] L. Vojáček, J. M. Dueñas, J. Li, et al., Nano Lett. 24, 11889 (2024)[14] M. Rassekh, M. Gmitra, Phys. Rev. B 113, 035126 (2026)