Abstract

All the iron-based superconductors identified so far share a square lattice composed of Fe atoms as a common feature, despite having different crystal structures. In copper-based materials, the superconducting phase emerges not only in square-lattice structures but also in ladder structures. Yet iron-based superconductors without a square-lattice motif have not been found, despite being actively sought out. Here, we report the discovery of pressure-induced superconductivity in the iron-based spin-ladder material BaFe2S3, a Mott insulator with striped-type magnetic ordering below 120 K. On the application of pressure this compound exhibits a metal–insulator transition at about 11 GPa, followed by the appearance of superconductivity below Tc = 14 K, right after the onset of the metallic phase. Our findings indicate that iron-based ladder compounds represent promising material platforms, in particular for studying the fundamentals of iron-based superconductivity.

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Acknowledgements

This work was partly supported by JSPS Grants-in-Aid for Scientific Research (A) (23244068), for Scientific Research (B) (23340097, 24340088 and 26287073) and for Young Scientists (B) (26800175), the Strategic Research Base Development Program for Private Universities (2009, S0901022) of MEXT and the Grant Program of the Yamada Science Foundation. The synchrotron radiation X-ray experiments were performed at BL-18C of KEK-PF under the approval of Proposal No. 2014G587.

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Affiliations

  1. College of Humanities & Sciences, Nihon University, Sakurajosui, Setagaya-ku, Tokyo 156-8550, Japan

    • Hiroki Takahashi
    • , Akira Sugimoto
    • , Takateru Kawakami
    • , Chizuru Kawashima
    •  & Hideto Soeda
  2. Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai, Miyagi 980-8577, Japan

    • Yusuke Nambu
    •  & Taku J. Sato
  3. Institute for Materials Research, Tohoku University, Sendai, Miyagi 980-8577, Japan

    • Yusuke Nambu
  4. Institute for Solid State Physics (ISSP), University of Tokyo, Kashiwa, Chiba 277-8581, Japan

    • Touru Yamauchi
    • , Yasuyuki Hirata
    • , Kazuyuki Matsubayashi
    • , Fei Du
    • , Yoshiya Uwatoko
    • , Yutaka Ueda
    •  & Kenya Ohgushi
  5. Bragg Institute, Australian Nuclear Science and Technology Organisation, Locked Bag 2001 Kirrawee DC, New South Wales 2232, Australia

    • Maxim Avdeev
  6. School of Chemistry, The University of Sydney, Sydney, New South Wales 2006, Australia

    • Maxim Avdeev
  7. Key laboratory of Physics and Technology for Advanced Batteries (Ministry of Education), College of Physics, Jilin University, Changchun 130012, China

    • Fei Du
  8. Ultra-High Pressure Processes Group, National Institute for Materials Science, Tsukuba, Ibaraki 305-0044, Japan

    • Satoshi Nakano
  9. Toyota Physical and Chemical Research Institute, Nagakute, Aichi 480-1192, Japan

    • Yutaka Ueda
  10. Department of Physics, Tohoku University, Sendai, Miyagi 980-8578, Japan

    • Kenya Ohgushi

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Contributions

H.T., Y.N. and K.O. designed the research; Y.H., F.D., Y.Ueda and K.O. synthesized the samples and performed the resistivity, magnetic-susceptibility and specific-heat measurements; M.A., Y.N. and T.J.S. performed the neutron-diffraction measurements and analysed the data; T.K. performed the Mössbauer measurements; A.S., C.K., H.S. and H.T. performed the resistivity measurements under high pressure at zero magnetic field; A.S., C.K., H.T., K.M. and Y.Uwatoko performed the resistivity measurements under high pressure at finite magnetic fields; T.Y. performed the resistivity and magnetic-susceptibility measurements under high pressure using the cubic anvil press; and C.K., S.N. and H.T. performed the X-ray diffraction measurements under high pressure. All the authors discussed the results. H.T., Y.N., T.K. and K.O. wrote the paper and all the authors read and commented on the manuscript.

Competing interests

The authors declare no competing financial interests.

Corresponding authors

Correspondence to Hiroki Takahashi or Kenya Ohgushi.

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DOI

https://doi.org/10.1038/nmat4351