Twist-angle dependent proximity induced spin-orbit coupling in graphene/topological insulator heterostructures

Abstract

The proximity-induced spin-orbit coupling (SOC) in heterostructures of twisted graphene and topological insulators (TIs) Bi${}_2$Se${}_3$ and Bi${}_2$Te${}_3$ is investigated from first principles. To build commensurate supercells, we strain graphene and correct thus resulting band offsets by applying a transverse electric field. We then fit the low-energy electronic spectrum to an effective Hamiltonian that comprises orbital and spin-orbit terms. For twist angles 0${}^{\circ }\le \Theta ⪅20^{\circ }$, we find the dominant spin-orbit couplings to be of the valley-Zeeman and Rashba types, both a few meV strong. We also observe a sign change in the induced valley-Zeeman SOC at $\Theta \approx 10^{\circ }$. Additionally, the in-plane spin structure resulting from the Rashba SOC acquires a non-zero radial component, except at $0^{\circ }$ or $30^{\circ }$. At $30^{\circ }$ the graphene Dirac cone interacts directly with the TI surface state. We therefore explore this twist angle in more detail, studying the effects of gating, TI thicknesses, and lateral shifts on the SOC parameters. We find, in agreement with previous results, the emergence of the proximitized Kane-Mele SOC, with a change in sign possible by electrically tuning the Dirac cone within the TI bulk band gap.

arXiv comment16 pages, 9 figures, 5 tables

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Cited by in corpus (12)

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• Giant asymmetric proximity-induced spin-orbit coupling in twisted graphene/SnTe heterostructure
• Moire-enabled topological superconductivity in twisted bilayer graphene
• Theory of weak localization in graphene with spin-orbit interaction
• Magnetoresistance in Noncentrosymmetric Two-dimensional Systems
• Transport Signatures of Radial Rashba Spin-Orbit Coupling at Ferromagnet/Superconductor Interfaces
• Chiral spin channels in curved graphene $pn$ junctions
• Ferroelectric switching control of spin current in graphene proximitized by In${}_2$Se${}_3$
• Topological phases, van Hove singularities, and spin texture in magic-angle twisted bilayer graphene in the presence of proximity-induced spin-orbit couplings
• Room-temperature spin-lifetime anisotropy exceeding 60 in bilayer graphene spin valves proximity coupled to WSe${}_2$
• Radial Rashba spin-orbit fields in commensurate twisted transition-metal dichalcogenide bilayers
• Interplay of Rashba and valley-Zeeman splittings in weak localization of spin-orbit coupled graphene