Epitaxial stabilization of (111)-oriented frustrated quantum pyrochlore thin films

Frustrated rare-earth pyrochlore titanates, Yb₂Ti₂O₇ and Tb₂Ti₂O₇, have been introduced as promising candidates to realize quantum spin ice (QSI). Multiple unusual quantum phases, including Coulombic ferromagnet, quantum valence bond solid, and quadrupolar ordering, have been predicted to emerge in the QSI state upon applying a (111)-oriented external magnetic field. Here, we report on the successful layer-by-layer growth of high-quality  thin films of the frustrated quantum pyrochlores, R₂Ti₂O₇ (R = Er, Yb, and Tb), along the (111) direction. We confirm their high crystallinity and proper chemical composition by in-situ RHEED, x-ray diffraction, reciprocal space mapping, transmission electron microscopy, and x-ray photoelectron spectroscopy. We discovered a robust mode of growth for Er₂Ti₂O₇ and Yb₂Ti₂O₇, and observed  a pressure-sensitive growth for Tb₂Ti₂O₇. The availability of large area (111)-oriented QSI structures with planar geometry offers a new complementary to the bulk platform to explore the strain and the magnetic field-dependent properties in the quasi-2D limit.