Atomic-Layer Controlled Transition from Inverse Rashba-Edelstein Effect to Inverse Spin Hall Effect in Two-Dimensional PtSe 2 Probed by THz Spintronic Emission.

Two-dimensional (2D) materials, such as transition metal dichalcogenides (TMDs), are ideal platforms for spin-charge conversion (SCC) as they possess strong spin-orbit coupling (SOC), reduced dimensionality and crystal symmetries as well as tuneable band structure, compared to metallic structures. Moreover, SCC can be tuned with the number of layers, electric field or strain. Here, we study spin-to-charge conversion in epitaxially grown 2D PtSe 2 by THz spintronic emission since its 1T crystal symmetry and strong SOC favor SCC. High quality of as-grown PtSe 2 layers is demonstrated, followed by in-situ ferromagnet deposition by sputtering that leaves the PtSe 2 unaffected, resulting in well-defined clean interfaces as evidenced with extensive characterization. Through this atomic growth control and using THz spintronic emission, the unique thickness dependent electronic structure of PtSe 2 allows the control of SCC. Indeed, we demonstrate the transition from the inverse Rashba-Edelstein effect (IREE) in 1-3 monolayers (ML) to the inverse spin Hall effect (ISHE) in multilayers (>3 ML) of PtSe 2 enabling the extraction of the perpendicular spin diffusion length and relative strength of IREE and ISHE. This band structure flexibility makes PtSe 2 an ideal candidate to explore the underlying mechanisms and engineering of the SCC but also to develop tuneable THz spintronic emitters. This article is protected by copyright. All rights reserved.