Molecular beam epitaxy of superconducting Sn 1 − x In x Te thin films

We report a systematic study on the growth conditions of ${\mathrm{Sn}}_{1\text{\ensuremath{-}}x}{\mathrm{In}}_{x}\mathrm{Te}$ thin films by molecular beam epitaxy for maximization of superconducting transition temperature ${T}_{\mathrm{c}}$. Careful tuning of the flux ratios of Sn, In, and Te enables us to find an optimum condition for substituting rich In content $(x=0.66)$ into the Sn site in a single phase of ${\mathrm{Sn}}_{1\text{\ensuremath{-}}x}{\mathrm{In}}_{x}\mathrm{Te}$ beyond the bulk solubility limit at ambient pressure $(x=0.5)$. ${T}_{\mathrm{c}}$ shows a dome-shaped dependence on In content $x$ with the highest ${T}_{\mathrm{c}}=4.20\phantom{\rule{0.16em}{0ex}}\mathrm{K}$ at $x=0.55$, being consistent to that reported for bulk crystals. The well-regulated ${\mathrm{Sn}}_{1\text{\ensuremath{-}}x}{\mathrm{In}}_{x}\mathrm{Te}$ films can be a useful platform to study possible topological superconductivity by integrating them into the state-of-the-art junctions and/or proximity-coupled devices.