Spin-to-charge conversion in Ferroelectric interfaces probed by THz-TDS

Recent studies using Terahertz Time-Domain Spectroscopy (THz-TDS) with spintronic emitters as a source have revealed distinct signatures of the Rashba effect, which arises from the breaking of inversion symmetry in low-dimensional materials and has been studied in heterostructures like CoFeB/PtSe2/MoSe2/LiNbO3 [1]. The observed phenomena are the source of the generated THz far-field emission, typically through mechanisms such as spin-to-charge conversion triggered by the absorption of ultrafast optical pulses. By using first-principles simulations, I will describe how to quantify the Rashba effect at PtSe2/MoSe2/LiNbO3 and HfO/Ni interfaces, expanding the traditional understanding of spin transport by incorporating the orbital degree of freedom. Moreover, we quantify the degree of control over the THz emission depending on the polarization direction of LiNbO3. In order to achieve this, we analyze the accumulation of both spin and orbital components using linear response theory, revealing distinct behaviors. At the same time, unlike the typical interaction observed between itinerant spins and magnetization in heavy metal/ferromagnet (HM/FM) interfaces [2,3], the orbital counterpart exhibits a distinct entanglement between the material’s orbital characteristics and the transport environment. Following this argument, I will show how the lattice that interacts strongly with the orbital degree of freedom can be effectively utilized in future spintronic devices [4,5].

[1] S. Massabeau et al., APL Mater. 13, 041102, 2025

[2] A. Pezo et al. Phys. Rev. B 112, 214426

[3] A. Pezo et al . Phys. Rev. B 111, 134424

[4] Tetsuya Sato et al .Phys. Rev. Lett. 137, 066302

[5] A. Pezo et al. arXiv.2605.03486

Armando Pezo is a Postdoctoral Fellow at the Institute for Solid State Physics, University of Tokyo. He earned his Ph.D. in Physics at the Universidade Federal do ABC (Brazil). Following this, he completed a postdoctoral position in the group of Aurélien Manchon at Aix-Marseille University and the Albert Fert Laboratory. His research interests span condensed matter theory and spintronics, with a focus on applying numerical techniques to study transport properties in quantum materials.

Séminaire organisé dans le cadre du programme interdisciplinaire MAT-PULSE