Imaging orbital-selective quasiparticles in the Hund’s metal state of FeSe

Abstract

Strong electronic correlations, emerging from the parent Mott insulator phase, are key to copper-based high-temperature superconductivity. By contrast, the parent phase of an iron-based high-temperature superconductor is never a correlated insulator. However, this distinction may be deceptive because Fe has five actived d orbitals while Cu has only one. In theory, such orbital multiplicity can generate a Hund’s metal state, in which alignment of the Fe spins suppresses inter-orbital fluctuations, producing orbitally selective strong correlations. The spectral weights Zm of quasiparticles associated with different Fe orbitals m should then be radically different. Here we use quasiparticle scattering interference resolved by orbital content to explore these predictions in FeSe. Signatures of strong, orbitally selective differences of quasiparticle Zm appear on all detectable bands over a wide energy range. Further, the quasiparticle interference amplitudes reveal that \(Z_{xy} < Z_{xz} \ll Z_{yz}\), consistent with earlier orbital-selective Cooper pairing studies. Thus, orbital-selective strong correlations dominate the parent state of iron-based high-temperature superconductivity in FeSe.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.

from$8.99

All prices are NET prices.

Fig. 1: Orbitally resolved quasiparticle scattering interference (QPI) in FeSe.
Fig. 2: Visualizing orbital-selective quasiparticle interference (QPI).
Fig. 3: Energy dependence of orbital-selective quasiparticle interference (QPI).
Fig. 4: Detecting orbital-selective QPI from both ε- and δ-bands above Fermi energy Ef.
Fig. 5: Momentum-angle dependence of OSQP weight Zm.

References

  1. 1.

    Dagotto, E. Correlated electrons in high-temperature superconductors. Rev. Mod. Phys. 66, 763 (1994).

    CAS  Article  Google Scholar 

  2. 2.

    Georges, A., Kotliar, G., Krauth, W. & Rozenberg, M. J. Dynamical mean-field theory of strongly correlated fermion systems and the limit of infinite dimensions. Rev. Mod. Phys. 68, 13 (1996).

    CAS  Article  Google Scholar 

  3. 3.

    Paglione, J. & Greene, R. L. High-temperature superconductivity in iron-based materials. Nat. Phys. 6, 645–658 (2010).

    CAS  Article  Google Scholar 

  4. 4.

    Wang, F. & Lee, D. H. The electron-pairing mechanism of iron-based superconductors. Science 332, 200–204 (2011).

    CAS  Article  Google Scholar 

  5. 5.

    Haule, K. & Kotliar, G. Coherence–incoherence crossover in the normal state of iron oxypnictides and importance of Hund’s rule coupling. New J. Phys. 11, 025021 (2009).

    Article  Google Scholar 

  6. 6.

    Yin, Z. P., Haule, K. & Kotliar, G. Kinetic frustration and the nature of the magnetic and paramagnetic states in iron pnictides and iron chalcogenides. Nat. Mater. 10, 932–935 (2011).

    CAS  Article  Google Scholar 

  7. 7.

    de’ Medici, L., Mravlje, J. & Georges, A. Janus-faced influence of Hund’s rule coupling in strongly correlated materials. Phys. Rev. Lett. 107, 256401 (2011).

    Article  Google Scholar 

  8. 8.

    Lanata, N. et al. Orbital selectivity in Hund’s metals: the iron chalcogenides. Phys. Rev. B 87, 045122 (2013).

    Article  Google Scholar 

  9. 9.

    Georges, A., de’ Medici, L. & Mravlje, J. Strong correlations from Hund’s coupling. Annu. Rev. Condens. Matter Phys. 4, 137–178 (2013).

    CAS  Article  Google Scholar 

  10. 10.

    de’ Medici, L., Giovannetti, G. & Capone, M. Selective Mott physics as a key to iron superconductors. Phys. Rev. Lett. 112, 177001 (2014).

    Article  Google Scholar 

  11. 11.

    Fanfarillo, L. & Bascones, E. Electronic correlations in Hund metals. Phys. Rev. B 92, 075136 (2015).

    Article  Google Scholar 

  12. 12.

    de’ Medici, L. & Capone, M. in F. Mancini, R. Citro (eds) The Iron Pnictide Superconductors. Springer Series in Solid-State Sciences 186 (Springer, Cham, 2017).

    Google Scholar 

  13. 13.

    de’ Medici, L. in The Physics of Correlated Insulators, Metals, and Superconductors (Modeling and Simulation Vol. 7) (eds Pavarini, E., Koch, E., Scalettar, R. & Martin, R.) 377–398 (Forschungszentrum Juelich, Juelich, 2017).

  14. 14.

    de’ Medici, L., Hassan, S. R., Capone, M. & Dai, X. Orbital-selective Mott transition out of band degeneracy lifting. Phys. Rev. Lett. 102, 126401 (2009).

    Article  Google Scholar 

  15. 15.

    Aichhorn, M., Biermann, S., Miyake, T., Georges, A. & Imada, M. Theoretical evidence for strong correlations and incoherent metallic state in FeSe. Phys. Rev. B 82, 064504 (2010).

    Article  Google Scholar 

  16. 16.

    Yu, R. & Si, Q. Mott transition in multiorbital models for iron pnictides. Phys. Rev. B 84, 235115 (2011).

    Article  Google Scholar 

  17. 17.

    Yu, R., Zhu, J.-X. & Si, Q. Orbital selectivity enhanced by nematic order in FeSe. Preprint at https://arxiv.org/abs/1803.01733 (2018).

  18. 18.

    Sprau, P. O. et al. Discovery of orbital-selective Cooper pairing in FeSe. Science 357, 75–80 (2017).

    CAS  Article  Google Scholar 

  19. 19.

    Kreisel, A. et al. Orbital selective pairing and gap structures of iron-based superconductors. Phys. Rev. B 95, 174504 (2017).

    Article  Google Scholar 

  20. 20.

    Arakawa, N. & Ogata, M. Orbital-selective superconductivity and the effect of lattice distortion in iron-based superconductors. J. Phys. Soc. Jpn. 80, 074704 (2011).

    Article  Google Scholar 

  21. 21.

    Yu, R., Zhu, J. X. & Si, Q. Orbital-selective superconductivity, gap anisotropy, and spin resonance excitations in a multiorbital t-J 1-J 2 model for iron pnictides. Phys. Rev. B 89, 024509 (2014).

    Article  Google Scholar 

  22. 22.

    Yi, M., Zhang, Y., Shen, Z.-X. & Lu, D. Role of the orbital degree of freedom in iron-based superconductors. npj Quantum Mater. 2, 57 (2017).

    Article  Google Scholar 

  23. 23.

    Suzuki, Y. et al. Momentum-dependent sign inversion of orbital order in superconducting FeSe. Phys. Rev. B 92, 205117 (2015).

    Article  Google Scholar 

  24. 24.

    Watson, M. D. et al. Evidence for unidirectional nematic bond ordering in FeSe. Phys. Rev. B 94, 201107 (2016).

    Article  Google Scholar 

  25. 25.

    Watson, M. D., Haghighirad, A. A., Rhodes, L. C., Hoesch, M. & Kim, T. K. Electronic anisotropies revealed by detwinned ARPES measurements of FeSe. New J. Phys. 19, 103021 (2017).

    Article  Google Scholar 

  26. 26.

    Terashima, T. et al. Anomalous Fermi surface in FeSe seen by Shubnikov–de Haas oscillation measurements. Phys. Rev. B 90, 144517 (2014).

    Article  Google Scholar 

  27. 27.

    Watson, M. D. et al. Emergence of the nematic electronic state in FeSe. Phys. Rev. B 91, 155106 (2015).

    Article  Google Scholar 

  28. 28.

    Coldea, A. I. & Watson, M. D. The key ingredients of the electronic structure of FeSe. Annu. Rev. Condens. Matter Phys. 9, 125–146 (2018).

    CAS  Article  Google Scholar 

  29. 29.

    Capriotti, L., Scalapino, D. J. & Sedgewick, R. D. Wave-vector power spectrum of the local tunneling density of states: ripples in a d-wave sea. Phys. Rev. B 68, 014508 (2003).

    Article  Google Scholar 

  30. 30.

    Yuan, T., Figgins, J. & Morr, D. K. Hidden order transition in URu2Si2: evidence for the emergence of a coherent Anderson lattice from scanning tunneling spectroscopy. Phys. Rev. B 86, 035129 (2012).

    Article  Google Scholar 

  31. 31.

    Lee, J. et al. Heavy d-electron quasiparticle interference and real-space electronic structure of Sr3Ru2O7. Nat. Phys. 5, 800–804 (2009).

    CAS  Article  Google Scholar 

  32. 32.

    Schmidt, A. R. et al. Imaging the Fano lattice to ‘hidden order’ transition in URu2Si2. Nature 465, 570–576 (2010).

    CAS  Article  Google Scholar 

  33. 33.

    Allan, M. P. et al. Imaging Cooper pairing of heavy fermions in CeCoIn5. Nat. Phys. 9, 468–473 (2013).

    CAS  Article  Google Scholar 

  34. 34.

    Kasahara, S. et al. Field-induced superconducting phase of FeSe in the BCS–BEC cross-over. Proc. Natl Acad. Sci. USA 111, 16309 (2014).

    CAS  Article  Google Scholar 

  35. 35.

    Watashige, T. et al. Evidence for time-reversal symmetry breaking of the superconducting state near twin-boundary interfaces in FeSe revealed by scanning tunneling spectroscopy. Phys. Rev. X 5, 031022 (2015).

    Google Scholar 

Download references

Acknowledgements

We are grateful to S.D. Edkins, A. Georges, M.H. Hamidian, J.E. Hoffman, G. Kotliar, E.-A. Kim, D.-H. Lee, L. de Medici, P. Phillips and J.-H. She for helpful discussions and communications. J.C.S.D. and P.C.C. acknowledge support from the Moore Foundation’s EPiQS (Emergent Phenomena in Quantum Physics) Initiative through Grant No. GBMF4544 and Grant No. GBMF4411, respectively. P.J.H. acknowledges support from DOE Grant No. DE-FG02-05ER46236. A.Kr. and B.M.A. acknowledge support from a Lundbeckfond Fellowship (Grant No. A9318). Material synthesis and detailed characterization at Ames National Laboratory was supported by the U.S. Department of Energy, Office of Basic Energy Science, Division of Materials Sciences and Engineering—Ames Laboratory is operated for the U.S. Department of Energy by Iowa State University under Contract No. DE-AC02-07CH11358; experimental studies carried out by the Center for Emergent Superconductivity, an Energy Frontier Research Center, headquartered at Brookhaven National Laboratory, were funded by the U.S. Department of Energy under Contract No. DE-2009-BNL-PM015.

Author information

Affiliations

Authors

Contributions

A.Ko., Y.X.C. and P.O.S. developed and carried out the experiments; A.E.B. and P.C.C. synthesized and characterized the samples; A.Ko., P.O.S. and A.Kr. developed and carried out analysis; A.Kr., B.M.A. and P.J.H. provided theoretical guidance; B.M.A., P.J.H. and J.C.S.D. supervised the project and wrote the paper with key contributions from A.Ko., Y.X.C., P.O.S., A.Kr, and P.J.H. The manuscript reflects the contributions and ideas of all authors.

Corresponding author

Correspondence to J. C. Séamus Davis.

Ethics declarations

Competing interests

The authors declare no competing interests.

Additional information

Publisher’s note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Supplementary information

Supplementary Information

Supplementary Text, Supplementary Figures 1–22, Supplementary Video Captions 1–5, Supplementary References 1–18

Supplementary Video 1

Simulation of quasiparticle interference patterns assuming a fully coherent band structure. Video shows from energy E = –25meV to E = 25 meV in 1.25 meV steps.

Supplementary Video 2

Simulation of quasiparticle interference patterns assuming orbitally selective quasiparticle weights. Video shows from energy E = –25 meV to E = 25 meV in 1.25 meV steps.

Supplementary Video 3

Measured quasiparticle interference pattern. Video shows from energy E = –25 meV to E = 25 meV in 1.25 meV steps.

Supplementary Video 4

Measured quasiparticle interference pattern in real space within –35 meV to +35 meV energy range acquired with 1 meV spacing at 4.2 K (<TC) and 10 K (>TC).

Supplementary Video 5

Video contains real space simulated and measured quasiparticle interference pattern within –25 meV to +25 meV energy range acquired with 1.25 meV spacing.

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Kostin, A., Sprau, P.O., Kreisel, A. et al. Imaging orbital-selective quasiparticles in the Hund’s metal state of FeSe. Nature Mater 17, 869–874 (2018). https://doi.org/10.1038/s41563-018-0151-0

Download citation

Further reading

Search

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing