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High-temperature superconductivity in potassium-coated multilayer FeSe thin films

Nature Materials volume 14, pages 775–779 (2015)Cite this article

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Abstract

The recent discovery of possible high-temperature (Tc) superconductivity over 65 K in a monolayer FeSe film on SrTiO3 (refs 1, 2, 3, 4, 5, 6) triggered a fierce debate on how superconductivity evolves from bulk to film, because bulk FeSe crystal exhibits a Tc of no higher than 10 K (ref. 7). However, the difficulty in controlling the carrier density and the number of FeSe layers has hindered elucidation of this problem4,8. Here, we demonstrate that deposition of potassium onto FeSe films markedly expands the accessible doping range towards the heavily electron-doped region. Intriguingly, we have succeeded in converting non-superconducting films with various thicknesses into superconductors with Tc as high as 48 K. We also found a marked increase in the magnitude of the superconducting gap on decreasing the FeSe film thickness, indicating that the interface plays a crucial role in realizing the high-temperature superconductivity. The results presented provide a new strategy to enhance and optimize Tc in ultrathin films of iron-based superconductors.

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Figure 1: Evolution of electronic structure on K deposition on a 3 ML FeSe film.
Figure 2: High-temperature superconductivity in a 3 ML FeSe film.
Figure 3: Electronic phase diagrams for different film thickness.

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Acknowledgements

We thank Q. Xue, X. Ma, L. Wang, F. Li and W. Zhang for their advice in thin-film growth. We also thank E. Ieki, G. N. Phan, S. Kanayama and E. Noguchi for their assistance in thin-film growth and ARPES measurements. This work was supported by grants from the Japan Society for the Promotion Science (JSPS) and the Ministry of Education, Culture, Sports, Science and Technology (MEXT) of Japan.

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Authors and Affiliations

  1. Department of Physics, Tohoku University, Sendai 980-8578, Japan

    Y. Miyata, K. Nakayama, T. Sato & T. Takahashi

  2. WPI Research Center, Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan

    K. Sugawara & T. Takahashi

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  1. Y. Miyata
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  2. K. Nakayama
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Contributions

Y.M., K.N. and T.T. designed the research. Y.M., K.N., K.S. and T.S. carried out the experiment. Y.M., K.N., T.S. and T.T. wrote the manuscript.

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Correspondence to K. Nakayama.

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Miyata, Y., Nakayama, K., Sugawara, K. et al. High-temperature superconductivity in potassium-coated multilayer FeSe thin films. Nature Mater 14, 775–779 (2015). https://doi.org/10.1038/nmat4302

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