Molecular beam epitaxy of a half-Heusler topological superconductor candidate YPtBi

The search for topological superconductivity has motivated investigations into materials that combine topological and superconducting properties. The half-Heusler compound YPtBi appears to be such a material; however, experiments have thus far been limited to bulk single crystals, drastically limiting the scope of available experiments. This has made it impossible to investigate the potential topological nature of the superconductivity in this material. Experiments to access details about the superconducting state require sophisticated lithographic structures, typically based on thin films. Here we report on the establishment of high-crystalline-quality epitaxial thin films of YPtBi(111), grown using molecular beam epitaxy on Al2O3(0001) substrates. A robust superconducting state is observed, with both critical temperature and critical field consistent with that previously reported for bulk crystals. Moreover, we find that AlOx capping sufficiently protects the sample surface from degradation to allow for proper lithography. Our results pave a path towards the development of advanced lithographic structures, which will allow the exploration of the potentially topological nature of superconductivity in YPtBi.