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Abstract : Novel operational scheme of devices can be envisioned if an efficient charge to spin current interconversion can be achieved in non-magnetic materials. In this presentation we will focus on experiments taking advantage of spin orbit coupling and realizing spin to charge conversion at the surface of topological insulators. We will also compare their efficiency, and interest, respect to more conventional Spin Hall and Rashba Edelstein effects. The spin Hall Effect occurs in material’s bulk. We will show that incorporating impurities in a matrix [1] could allow the fine tuning of the resistivity, the spin diffusion length (lsf) and the spin Hall angle (SHA) of alloys. Moreover, by taking advantage of the side jump contribution, the SHA becomes dependent on the longitudinal resistivity, and very large SHA can be achieved at high impurity concentration, reaching 0.5 (or 50%) in our best case. Interfaces can also be an efficient way to perform charge to spin conversion using the Rashba interaction. Following our first experimental observation on Ag/Bi bilayers [2], we studied the 2D electron system that exists at the interface between STO and LAO. We will show that the Rashba-Edelstein effect at low temperature is at least one order of magnitude larger in this system and can be tuned by an external gate, leading even to its sign reversal [3]. We will then discuss the case of Topological Insulators and on the importance of finding suitable heterostructures that preserve the topological states. We will present results on strained thin films of Sn and HgTe. These material has been recently predicted to be a Topological Insulator as confirmed by spectroscopy measurements. Interestingly we could achieved unprecedented conversion rates at room temperature in these systems [4]. Finally we will give some elements to draw an appropriate comparison between these different systems and physical mechanisms, in order to identify best candidates for future spintronics devices.

[1] P. Laczkowski et al. Appl. Phys. Lett. 104, 142403 (2014) ; Phys. Rev. Lett. under review

[2] J.C. Rojas Sanchez et al. Nat. Commun. 4:2944 doi : 10.1038/ncomms3944 (2013)

[3] E. Lesne et al, Nat. Mat. 15, 1261 (2016), DOI : 10.1038/NMAT4726

[4] J.C. Rojas Sanchez et al, Phys. Rev. Lett. 116, 096602 (2016)

Contact : Laurent Vila