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Quasiparticle interference and strong electron–mode coupling in the quasi-one-dimensional bands of Sr2RuO4

Nature Physics volume 13, pages 799805 (2017) | Download Citation

Abstract

The single-layered ruthenate Sr2RuO4 is presented as a potential spin-triplet superconductor with an order parameter that may break time-reversal invariance and host half-quantized vortices with Majorana zero modes. Although the actual nature of the superconducting state is still a matter of controversy, it is believed to condense from a metallic state that is well described by a conventional Fermi liquid. In this work we use a combination of Fourier transform scanning tunnelling spectroscopy (FT-STS) and momentum-resolved electron energy loss spectroscopy (M-EELS) to probe interaction effects in the normal state of Sr2RuO4. Our high-resolution FT-STS data show signatures of the β-band with a distinctly quasi-one-dimensional (1D) character. The band dispersion reveals surprisingly strong interaction effects that dramatically renormalize the Fermi velocity, suggesting that the normal state of Sr2RuO4 is that of a ‘correlated metal’ where correlations are strengthened by the quasi-1D nature of the bands. In addition, kinks at energies of approximately 10 meV, 38 meV and 70 meV are observed. By comparing STM and M-EELS data we show that the two higher energy features arise from coupling with collective modes. The strong correlation effects and the kinks in the quasi-1D bands could provide important information for understanding the superconducting state.

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Acknowledgements

We thank Z. Wang, H. Lin, J.C.  Davis and S. Kivelson for useful conversations. STM work was supported by US Department of Energy, Scanned Probe Division under Award Number DE-SC0014335. The work was supported in part by the Gordon and Betty Moore Foundation’s EPiQS Initiative through Grant GBMF4860. Y.M. acknowledges the support from the JSPS KAKENHI Grant No. JP15H05852. Theoretical work was supported in part by the Gordon and Betty Moore Foundation’s EPiQS Initiative through Grant No. GBMF4305 at the Institute for Condensed Matter Theory of the University of Illinois (L.H.S. and Y.W.), and by a grant of the National Science Foundation No. DMR1408713 at the University of Illinois (E.F.). M-EELS experiments were supported by the Center for Emergent Superconductivity, DOE #DE-AC02-98CH10886. P.A. acknowledges support from Gordon and Betty Moore Foundation’s EPiQS Initiative through Grant GBMF4542. T.S. acknowledges the financial support of the Clarendon Fund Scholarship, the Merton College Domus and Prize Scholarships, and the University of Oxford.

Author information

Author notes

    • Zhenyu Wang
    •  & Daniel Walkup

    These authors contributed equally to this work.

Affiliations

  1. Department of Physics and Frederick Seitz Materials Research Laboratory, University of Illinois Urbana-Champaign, Urbana, Illinois 61801, USA

    • Zhenyu Wang
    • , Melinda Rak
    • , Sean Vig
    • , Anshul Kogar
    • , Ali Husain
    • , Peter Abbamonte
    •  & Vidya Madhavan
  2. Department of Physics, Boston College, Chestnut Hill, Massachusetts 02467, USA

    • Daniel Walkup
    •  & Ilija Zeljkovic
  3. National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA

    • Daniel Walkup
  4. Department of Chemistry, Physical & Theoretical Chemistry, Oxford University, South Parks Road, Oxford OX1 3QZ, United Kingdom

    • Philip Derry
  5. Rudolf Peierls Centre for Theoretical Physics, Oxford OX1 3NP, UK

    • Thomas Scaffidi
  6. Department of Physics and Institute for condensed Matter Theory, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA

    • Luiz H. Santos
    • , Yuxuan Wang
    •  & Eduardo Fradkin
  7. Department of Physics & Astronomy, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada

    • Andrea Damascelli
  8. Quantum Matter Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada

    • Andrea Damascelli
  9. Department of Physics, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan

    • Yoshiteru Maeno

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Contributions

Z.W. and D.W. contributed equally to this work. Z.W., D.W. and V.M. designed the STM experiments, analysed the data and wrote the paper. STM experiments were performed by D.W., Z.W. and I.Z. Y.M. was responsible for single-crystal growth and structural analysis. A.D. helped with conceiving the experiment, data analysis and comparison with ARPES. E.F., L.H.S. and Y.W. conceived the theoretical explanation for this work. P.D., and T.S. performed analytical model calculations. M.R., S.V., A.K., A.H. and P.A. were involved in the M-EELS studies.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Vidya Madhavan.

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DOI

https://doi.org/10.1038/nphys4107

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