Study of the charge current – spin current interconversion in Rashba-Edelstein interfaces and topological insulators surfaces

The conversion of a conventional charge current into a spin current, carrying not charges but angular momentum, can be done in non-magnetic systems using the spin-orbit coupling. Spin-dependent transport effects can thus be observed in very wide ranges of materials and interfaces, allowing spin manipulation in metals, oxides [1], semiconductors, Rashba interfaces, topological insulators, 2D materials, etc.

We will use the spin pumping phenomenon, which takes place at the ferromagnetic resonance, to inject a spin current from a ferromagnet into STO [2] and KTO-based Rashba systems [3], and into topological insulators such as HgTe [4] and Sb₂Te₃. The conversion of this spin current into a charge current will be detected electrically for different experimental parameters: temperature, gate voltage, layer thickness, presence of a tunnel barrier or of a metal layer, stoichiometry of the materials … This will allow studying the physics of spin-orbit coupling in these materials, such as the hybridization of surface states in topological insulators, or the role of interfaces in spin-dependent transport.

Once the optimal systems have been identified, nanodevices will be manufactured to realize this interconversion electrically (see Figure 1), in both possible directions (charge to spin or spin to charge). This subject is a rather fundamental research topic, with transport effects specific to spin-orbit coupling appearing in new materials. It could however lead to beyond-CMOS logic and/or memory devices.

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