In a new paper just published in Advanced Materials, we report the generation of two-dimensional electron gases (2DEGs) in KTaO3 (KTO) by the simple deposition of ultrathin Al films by sputtering at room temperature. As in our earlier studies on SrTiO3 2DEGs, we investigated the formation of the 2DEG in KTO in situ using X-ray photoelectron spectroscopy, and ex situ using magnetotransport. The advantage of KTO 2DEGs over STO 2DEGs lies notably in the larger expected spin-orbit coupling, because spin-orbit interaction scales strongly with atomic mass, and Ta is much heavier than Ti. We indeed found that our KTO 2DEGs display a strong Rashba spin-orbit coupling that we have harnessed to convert charge currents into spin currents and vice verse using the direct and inverse Edelstein effects, respectively. In the former case, we detected charge to spin conversion through unidirectional magnetoresistance measurements. In the latter case, we picked up the produced charge voltage after injecting spins from a NiFe layer through spin pumping. We found that the Rashba coefficient of KTO 2DEGs is larger than that of STO 2DEGs by a factor of at least 5, which opens exciting perspectives for their integration into spin-orbitronics architectures.

This work was done in collaboration with Spintec, Synchrotron SOLEIL, the LPEM of ESPCI and Intel Components Research.

Spin–Charge Interconversion in KTaO3 2D Electron Gases
Luis M. Vicente-Arche, Julien Bréhin, Sara Varotto, Maxen Cosset-Cheneau, Srijani Mallik, Raphaël Salazar, Paul Noël, Diogo C. Vaz, Felix Trier, Suvam Bhattacharya, Anke Sander, Patrick Le Fèvre, François Bertran, Guilhem Saiz, Gerbold Ménard, Nicolas Bergeal, Agnès Barthélémy, Hai Li, Chia-Ching Lin, Dmitri E. Nikonov, Ian A. Young, Julien E. Rault, Laurent Vila, Jean-Philippe Attané, Manuel Bibes
Adv. Mater. 202102102 (2021)