High-temperature superconductivity in atomic-layer FeSe films

We report angle-resolved photoemission spectroscopy (ARPES) study on atomic-layer FeSe films grown on SrTiO₃ substrate. We observed that a monolayer film shows superconductivity with the onset temperature of 60 K. We also found that potassium (K) deposition onto the film enables the systematic control of carrier concentration. By using this method, we have succeeded in converting non-superconducting as-grown multilayer films into a high-temperature superconductor. We have established the electronic phase diagram of FeSe film and revealed an important role of interface for realizing the high-temperature superconductivity. (author)