Yuki Sato, S. Nagahama, Shunsuke Kitou, Hajime Sagayama, Ilya Belopolski, Ryutaro Yoshimi, Minoru Kawamura, Atsushi Tsukazaki, Naoya Kanazawa, Takuya Nomoto, Ryotaro Arita, T. Arima, M. Kawasaki, Yoshinori Tokura
Molecular beam epitaxy enables the growth of thin film materials with novel properties and functionalities. Typically, the lattice constants of films and substrates are designed to match to minimise disorders and strains. However, significant lattice mismatches can result in higher-order epitaxy, where commensurate growth occurs with a period defined by integer multiples of the lattice constants. Despite its potential, higher-order epitaxy is rarely used to enhance material properties or induce emergent phenomena. Here, we report single-crystalline FeTe films grown via 6:5 commensurate higher-order epitaxy on CdTe(001) substrates. Scanning transmission electron microscopy reveals self-organised periodic interstitials near the interface, arising from higher-order lattice matching. Synchrotron x-ray diffraction shows that the tetragonal-to-monoclinic structural transition in bulk FeTe is strongly suppressed. Remarkably, these films exhibit substrate-selective two-dimensional superconductivity, likely due to suppressed monoclinic distortion. These findings demonstrate the potential of higher-order epitaxy as a tool to control materials and inducing emergent phenomena. The authors report crystalline FeTe films grown on CdTe(001) substrates. They find that 6 units of FeTe grow on 5 units of CdTe, a phenomenon known as commensurate higher-order epitaxy. In the resulting FeTe films, they find two-dimensional superconductivity that is absent in bulk FeTe, likely due to suppression of the monoclinic distortion.