Dr. David Soriano

Catalan Institute of Nanoscience and Nanotechnology (ICN2)

 Where: room 434 A, Building 10.05, CEA-Grenoble.

            The possibility to manipulate the magnetism at the atomic scale in 2D materials shown promising for the next generation of data storage devices and for quantum technologies. Hydrogenated graphene has demonstrated to be a good platform for such applications where the magnetic states can be modified using a STM tip [1]. At the same time, the presence of resonant states leading to local magnetic moments seems to be detrimental for spintronic applications since the spin relaxation time in presence of such states decreases to the order of picoseconds [2].

Inducing a strong spin-orbit coupling to graphene by metallic adatoms[3] or by deposition on heavy metals or topological insulators is attracting a lot of interest. The long mean free path found in graphene makes it an ideal platform to properly detect the spin currents induced by the spin Hall effect [4]. Also, a giant spin-orbit torque effect has been recently predicted intercalating single layer or bilayer graphene between a topological insulator and a ferromagnet [5].

In the first part of this seminar I will show recent calculations where we demonstrate that hydrogenated polycrystalline graphene is less sensitive to hydrogenation than pristine graphene. The grain boundaries are more reactive towards hydrogen adsorption and eventually they act as resonant states sinks induced by the local absence of sublattice symmetry.

The second part will focus on recent first-principles calculations carried out in our group based on Graphene-Bi₂Se₃ heterostructures. By fitting the band structure using a tight-binding model we are able to extract the intrinsic and Rashba spin-orbit coupling induced to the graphene layer by proximity effect. Our results are similar to those found recently on Graphene-WSe₂ heterostruture [6] but far from the ones published recently on Sb₂Te₃ [7]. I will discuss such controversy based on the influence of the chemical elements involved (Te vs Se) and the interaction between graphene and TI.

[1] González-Herrero et al. Science 352, 437 – 441 (2016)

[2] Kochan et al. Phys. Rev. Lett. 112, 116602 (2014)

[3] Cresti et al. Phys. Rev. Lett. 113, 246603 (2014)

[4] Vaklinova et al. Nano Lett. 16, 2595 – 2602 (2016)

[5] Rodriguez-Vela et al. arXiv:1610.04229

[6] Gmitra et al. Phys. Rev. B 93, 155104 (2016)

[7] Jin et al. Phys. Rev. B 87, 075442 (2013)