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Observation of a d-wave gap in electron-doped Sr2IrO4

Nature Physics volume 12, pages 37–41 (2016)Cite this article

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Abstract

High-temperature superconductivity in cuprates emerges out of a highly enigmatic ‘pseudogap’ metal phase. The mechanism of high-temperature superconductivity is probably encrypted in the elusive relationship between the two phases, which spectroscopically is manifested as Fermi arcs—disconnected segments of zero-energy states—collapsing into d-wave point nodes upon entering the superconducting phase. Here, we reproduce this distinct cuprate phenomenology in the 5d transition-metal oxide Sr2IrO4. Using angle-resolved photoemission, we show that the clean, low-temperature phase of 6–8% electron-doped Sr2IrO4 has gapless excitations only at four isolated points in the Brillouin zone, with a predominant d-wave symmetry of the gap. Our work thus establishes a connection between the low-temperature d-wave instability and the previously reported high-temperature Fermi arcs in electron-doped Sr2IrO4 (ref. 1). Although the physical origin of the d-wave gap remains to be understood, Sr2IrO4 is the first non-cuprate material to spectroscopically reproduce the complete phenomenology of the cuprates, thus offering a new material platform to investigate the relationship between the pseudogap and the d-wave gap.

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Figure 1: Low-temperature nodal Fermi surface and high-temperature Fermi arcs.
Figure 2: Temperature dependence of the gap.
Figure 3: Momentum dependence of the gap at T = 10 K.
Figure 4: Illustration of our materials scheme to access low-temperature spectral functions for electron-doped Sr2IrO4.

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Acknowledgements

We acknowledge helpful discussions with C. Kim, G. Khaliullin, B. Keimer, M. Le Tacon, G. Jackeli, J. F. Mitchell, M. Norman and J. W. Allen. We thank B. Y. Kim for technical assistance. The Advanced Light Source is supported by the Director, Office of Science, Office of Basic Energy Sciences, of the US Department of Energy under Contract No. DE-AC02-05CH11231. This work was supported by IBS-R009-D1.

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Author notes

  1. Y. K. Kim and N. H. Sung: These authors contributed equally to this work.

Authors and Affiliations

  1. Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA

    Y. K. Kim & J. D. Denlinger

  2. Center for Correlated Electron Systems, Institute for Basic Science, Seoul 151-742, South Korea

    Y. K. Kim

  3. Department of Physics and Astronomy, Seoul National University, Seoul 151-747, South Korea

    Y. K. Kim

  4. Max Planck Institute for Solid State Research, Heisenbergstraße 1, D-70569 Stuttgart, Germany

    N. H. Sung & B. J. Kim

Authors
  1. Y. K. Kim
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  2. N. H. Sung
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Contributions

B.J.K. conceived the project. Y.K.K. and B.J.K. performed the ARPES experiment with support from J.D.D. N.H.S. grew and characterized the single crystals. Y.K.K. analysed the data. All authors discussed the results. B.J.K. led the manuscript preparation with contributions from all authors.

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Correspondence to B. J. Kim.

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Kim, Y., Sung, N., Denlinger, J. et al. Observation of a d-wave gap in electron-doped Sr2IrO4. Nature Phys 12, 37–41 (2016). https://doi.org/10.1038/nphys3503

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