Speaker-Stephan Roche

Stephan Roche
Stephan Roche is ICREA Research Professor, head of the Theoretical and Computational Nanoscience Group of Catalan Institute of Nanoscience and Nanotechnology (ICN2). He is a theoretical physicist expert in quantum transport and in the development of computational modelling of nanomaterials and devices. His expertise includes the development of order N quantum transport (Kubo and Landauer-Büttiker conductances), with which he has pioneered mesoscopic transport studies in chemically disordered graphene-based materials and devices. He has a deep experience in developing advanced simulation tools in the context of industrial research, with collaborations including large companies such as NEC, ST Microelectronics, and SAMSUNG. He is co-supervising the GRAPHENE SPINTRONICS Work package within the Graphene Flagship project.
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The physics of graphene can be strongly enriched andmanipulated by harvesting the large amount of possibilities of proximityeffects with magnetic insulators, strong SOC materials (TMDC, topologicalinsulators, etc.). Simultaneously, the presence of extra degrees of freedom(sublattice pseudospin, valley isospin) points towards new directions forinformation processing [1,2], extending the playground to valleytronics,multifunctional electronic devices or novel quantum computing paradigmsharnessing all these degrees of freedom in combination with electromagneticfields or other external fields (strain, chemical functionalization)[3,4].

Here I will present some foundations of spin transport forDirac fermions propagating in supported graphene devices or interfaced withstrong SOC materials. The role of entanglement with “valley and sublatticepseudospins” in tailoring the spin dephasing and relaxation mechanisms will beexplained as well as the impact of strong SOC proximity effects on spinlifetime anisotropy, weak antilocalization and Spin Hall effect [4-8]. I willalso refute recent claims concerning the formation of the valley Hall effect ingraphene/hBN heterostructures which relate measured giant non-local resistancewith Berry curvature-induced bulk valley currents [9]. Such analysis isfundamentally flawed, whereas the understanding of non-local transportproperties requires advanced and realistic quantum transport calculations (seerecent advances published in [10]).

[1] S. Roche et al. 2D Materials 2, 030202 (2015).

[2] D.V. Tuan et al. Nature Physics 10,857 (2014).

[3] D.V. Tuan & S. Roche, Phys. Rev. Lett. 116, 106601 (2016).

[4] A.W.Cummings, J. H. García, J. Fabian and S. Roche, Phys. Rev. Lett. 119,206601 (2016).

[5] J.H. García, A.W. Cummings, S. Roche, Nano Lett. 17 (8),5078–5083 (2017).

[6] K. Song, D. Soriano, A.W. Cummings, R. Robles, P. Ordejón & S. Roche, Nanolett. 18 (3), 2033 (2018).

[7] J.H. García, M. Vila, A.W. Cummings & S. Roche, Chem.Soc. Rev. 47, 3359-3379 (2018).

[8] D. Khokhriakov, A.W. Cummings, M. Vila, B. Karpiak, A. Dankert,

S.Roche & S.P. Dash, Science Advances (in press)

[9] A. Cresti et al. Riv. Nuovo Cimento 39, 587 (2018).

[10] J. M. Marmolejo-Tejada et al.,arXiv:1706.09361; J. Phys. Materials (in press).

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E-mail: meeting@c-gia.org

Abstract: Minyang Lu

Sponsor: Wenyang Yang

Media: Liping Wang

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