Speaker
Description
Topological insulators (TIs) represent a state of matter in which the material bulk has insulating properties while the surface hosts highly conducting states [1]. In TIs, the presence of Dirac-like dispersed surface states jointly with the large spin–orbit coupling provides the so-called spin-momentum locking and generates topologically protected surface states [1]. Within this talk I will first present the basics of TIs with particular focus on the properties making them appealing from a technological perspective [2,3]. I will then present our strategies to develop epitaxial quality chalcogenide-based 3D-TIs over large area (up to 4”) Si substrates by means of Metal Organic Chemical Vapour Deposition [4-7]. Following the validation of their topological character [7], I will present how we built simple spin-charge converters by interfacing the TIs with ferromagnetic layers (FM=Fe,Co). In such TI/FM systems, we report a large spin-charge conversion efficiency, as measured by spin pumping ferromagnetic resonance (SP-FMR) [8,9]. More recently, we developed combined Sb2Te3/Bi2Te3 heterostructures, where the top Bi2Te3 layer displays a remarkable shift of the Fermi level towards the Dirac point, as visualized by angular resolved photoemission spectroscopy [10]. This led to an almost total suppression of bulk states’ contribution resulting in the emergence of ideal topologically-protected surfaces states, which are successfully exploited to enhance the spin-charge conversion efficiency when compared to single layer-TIs [10]. Our results open interesting routes toward the use of chemical methods to produce TIs over large area Si substrates, which may bring them closer to the future technology-transfer of spintronic devices based on them.
[1] 1M. Z. Hasan, C. L. Kane, Rev. Mod. Phys. 82, 3045 (2010)
[2] H. Wu et al., Nat. Comm 12, 6251 (2021)
[3] S. Manipatruni et al., Nature 565, 35 (2019)
[4] M. Rimoldi et al., RCS Advances 10, 19936 (2020)
[5] M. Rimoldi et al., Cryst. Growth Des. 21, 5135 (2021)
[6] A Kumar et al., Cryst. Growth Des.21, 4023 (2021)
[7] L. Locatelli et al., Scientific Reports 12, 3891 (2022)
[8] E. Longo et al., Adv. Mater. Interfaces 8, 2101244 (2021)
[9] E. Longo et al., Adv. Funct. Mater. 32, 2109361 (2021)
[10] E. Longo et al., ACS Appl. Mater. Interfaces (accepted, 2023)
