Testing the topological insulator behavior of half-Heusler PdYBi and PtYBi (111) epitaxial thin films

Topological insulators are promising materials in condensed-matter physics on the grounds that they host a peculiar spin texture that can generate very high spin-to-charge current interconversion, significantly relevant for up-and-coming low-energy-consumption spintronics devices. The goal of this study is to explore a promising family of topological materials showing distinctive properties such as high tunability-the half-Heuslers. We focus on the epitaxial growth of PdYBi and PtYBi thin films, which were grown and characterized on a series of interconnected UHV setups, allowing us to get a full set of in situ surface characterizations, such as electron diffraction, scanning tunneling microscopy, and angle-resoled photoemission spectroscopy. Ex situ structural characterization using standard x-ray diffraction and scanning transmission electron microscopy were used to control the crystalline quality and chemical ordering in the thin films. Angle-resolved photoemission spectroscopy was performed and reveals the presence of linear states around the point of the Brillouin zone. Furthermore, we carry out thermospin transport measurements using on-chip devices with a designed geometry for a controlled heat propagation to test the potential interconversion efficiency of our compounds, finding a larger value of the spin Seebeck coefficient than that of platinum for different thicknesses for both PdYBi and PtYBi. This observation opens a pathway to develop efficient spin interconversion materials using half-Heuslers.