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Universality of pseudogap and emergent order in lightly doped Mott insulators

Nature Physics volume 13, pages 21–25 (2017)Cite this article

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Abstract

It is widely believed that high-temperature superconductivity in the cuprates emerges from doped Mott insulators1. When extra carriers are inserted into the parent state, the electrons become mobile but the strong correlations from the Mott state are thought to survive—inhomogeneous electronic order, a mysterious pseudogap and, eventually, superconductivity appear. How the insertion of dopant atoms drives this evolution is not known, nor is whether these phenomena are mere distractions specific to hole-doped cuprates or represent genuine physics of doped Mott insulators. Here we visualize the evolution of the electronic states of (Sr1−xLax)2IrO4, which is an effective spin-1/2 Mott insulator like the cuprates, but is chemically radically different2,3. Using spectroscopic-imaging scanning tunnelling microscopy (SI-STM), we find that for a doping concentration of x ≈ 5%, an inhomogeneous, phase-separated state emerges, with the nucleation of pseudogap puddles around clusters of dopant atoms. Within these puddles, we observe the same iconic electronic order that is seen in underdoped cuprates1,4,5,6,7,8,9. We investigate the genesis of this state and find evidence at low doping for deeply trapped carriers, leading to fully gapped spectra, which abruptly collapse at a threshold of x ≈ 4%. Our results clarify the melting of the Mott state, and establish phase separation and electronic order as generic features of doped Mott insulators.

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Figure 1: The lightly doped effective Mott insulator (Sr1−xLax)2IrO4.
Figure 2: The electronic structure of (Sr1−xLax)2IrO4 at low doping.
Figure 3: Phase-separated Mott/pseudogap electronic structure at 5.5% doping.
Figure 4: Nucleating order.
Figure 5: The evolution of the electronic structure with increasing dopant atom concentration.

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References

  1. Keimer, B., Kivelson, S. A., Norman, M. R., Uchida, S. & Zaanen, J. From quantum matter to high-temperature superconductivity in copper oxides. Nature 518, 179–186 (2015).

    Article  ADS  Google Scholar 

  2. Rau, J. G., Lee, E. K.-H. & Kee, H.-Y. Spin-orbit physics giving rise to novel phases in correlated systems: iridates and related materials. Annu. Rev. Condens. Matter Phys. 7, 195–221 (2016).

    Article  ADS  Google Scholar 

  3. Kim, B. J. et al. Novel Jeff = 1/2 Mott state induced by relativistic spin-orbit coupling in Sr2IrO4 . Phys. Rev. Lett. 101, 076402 (2008).

    Article  ADS  Google Scholar 

  4. Fujita, K. et al. Spectroscopic Imaging STM: Atomic-Scale Visualization of Electronic Structure and Symmetry in Underdoped Cuprates Ch. 3 (Springer, 2012).

    Google Scholar 

  5. Kohsaka, Y. et al. Imaging nanoscale electronic inhomogeneity in the lightly doped Mott insulator Ca2−xNaxCuO2Cl2 . Phys. Rev. Lett. 93, 097004 (2004).

    Article  ADS  Google Scholar 

  6. Cai, P. et al. Visualizing the evolution from the Mott insulator to a charge-ordered insulator in lightly doped cuprates. Nat. Phys. http://dx.doi.org/10.1038/nphys3840 (2016).

  7. Kohsaka, Y. et al. Visualization of the emergence of the pseudogap state and the evolution to superconductivity in a lightly hole-doped Mott insulator. Nat. Phys. 8, 534–538 (2012).

    Article  Google Scholar 

  8. Parker, C. V. et al. Fluctuating stripes at the onset of the pseudogap in the high-Tc superconductor Bi2Sr2CaCu2O8+x . Nature 468, 677–680 (2010).

    Article  ADS  Google Scholar 

  9. Comin, R. & Damascelli, A. Resonant X-ray scattering studies of charge order in cuprates. Annu. Rev. Condens. Matter Phys. 7, 369–405 (2016).

    Article  ADS  Google Scholar 

  10. Fradkin, E., Kivelson, S. A. & Tranquada, J. M. Colloquium: theory of intertwined orders in high temperature superconductors. Rev. Mod. Phys. 87, 457–482 (2015).

    Article  ADS  Google Scholar 

  11. Wang, F. A. & Senthil, T. Twisted Hubbard model for Sr2IrO4: magnetism and possible high temperature superconductivity. Phys. Rev. Lett. 106, 136402 (2011).

    Article  ADS  Google Scholar 

  12. Watanabe, H., Shirakawa, T. & Yunoki, S. Monte Carlo study of an unconventional superconducting phase in iridium oxide Jeff = 1/2 Mott insulators induced by carrier doping. Phys. Rev. Lett. 110, 027002 (2013).

    Article  ADS  Google Scholar 

  13. Okada, Y. et al. Imaging the evolution of metallic states in a correlated iridate. Nat. Mater. 12, 707–713 (2013).

    Article  ADS  Google Scholar 

  14. McElroy, K. et al. Atomic-scale sources and mechanism of nanoscale electronic disorder in Bi2Sr2CaCu2O8+δ . Science 309, 1048–1052 (2005).

    Article  ADS  Google Scholar 

  15. Zeljkovic, I. et al. Imaging the impact of single oxygen atoms on superconducting Bi2+ySr2−yCaCu2O8+x . Science 337, 320–323 (2012).

    Article  ADS  Google Scholar 

  16. Ye, C. et al. Visualizing the atomic-scale electronic structure of the Ca2CuO2Cl2 Mott insulator. Nat. Commun. 4, 1365 (2013).

    Article  ADS  Google Scholar 

  17. Feenstra, R. M., Dong, Y., Semtsiv, M. P. & Masselink, W. T. Influence of tip-induced band bending on tunnelling spectra of semiconductor surfaces. Nanotechnology 18, 044015 (2007).

    Article  ADS  Google Scholar 

  18. Wijnheijmer, A. P. et al. Single Si dopants in GaAs studied by scanning tunneling microscopy and spectroscopy. Phys. Rev. B 84, 125310 (2011).

    Article  ADS  Google Scholar 

  19. Moon, S. J. et al. Temperature dependence of the electronic structure of the Jeff 1/2 Mott insulator. Phys. Rev. B 80, 195110 (2009).

    Article  ADS  Google Scholar 

  20. Chen, X. et al. Influence of electron doping on the ground state of (Sr1−xLax)2IrO4 . Phys. Rev. B 92, 075125 (2015).

    Article  ADS  Google Scholar 

  21. Yan, Y. J. et al. Electron-doped Sr2IrO4: an analogue of hole-doped cuprate superconductors demonstrated by scanning tunneling microscopy. Phys. Rev. X 5, 041018 (2015).

    Google Scholar 

  22. Dai, J., Calleja, E., Cao, G. & McElroy, K. Local density of states study of a spin-orbit-coupling induced Mott insulator Sr2IrO4 . Phys. Rev. B 90, 041102 (2014).

    Article  ADS  Google Scholar 

  23. He, J. et al. Spectroscopic evidence for negative electronic compressibility in a quasi-three-dimensional spin-orbit correlated metal. Nat. Mater. 14, 577–582 (2015).

    Article  ADS  Google Scholar 

  24. Kim, Y. K. et al. Fermi arcs in a doped pseudospin-1/2 Heisenberg antiferromagnet. Science 345, 187–190 (2014).

    Article  ADS  Google Scholar 

  25. de la Torre, A. et al. Collapse of the Mott gap and emergence of a nodal liquid in lightly doped Sr2IrO4 . Phys. Rev. Lett. 115, 176402 (2015).

    Article  ADS  Google Scholar 

  26. Kim, Y. K., Sung, N. H., Denlinger, J. D. & Kim, B. J. Observation of a d-wave gap in electron-doped Sr2IrO4 . Nat. Phys. 12, 37–41 (2015).

    Article  Google Scholar 

  27. Alldredge, J. W. et al. Evolution of the electronic excitation spectrum with strongly diminishing hole density in superconducting Bi2Sr2CaCu2O8+δ . Nat. Phys. 4, 319–326 (2008).

    Article  Google Scholar 

  28. Civelli, M., Capone, M., Kancharla, S. S., Parcollet, O. & Kotliar, G. Dynamical breakup of the Fermi surface in a doped Mott insulator. Phys. Rev. Lett. 95, 106402 (2005).

    Article  ADS  Google Scholar 

  29. Mott, N. F. Metal-insulator transition. Rev. Mod. Phys. 40, 677–683 (1968).

    Article  ADS  Google Scholar 

  30. Kastner, M. A., Birgeneau, R. J., Shirane, G. & Endoh, Y. Magnetic, transport, and optical properties of monolayer copper oxides. Rev. Mod. Phys. 70, 897–928 (1998).

    Article  ADS  Google Scholar 

  31. Anisimov, V. I., Zaanen, J. & Andersen, O. K. Band theory and Mott insulators: Hubbard U instead of Stoner I. Phys. Rev. B 44, 943–954 (1991).

    Article  ADS  Google Scholar 

Download references

Acknowledgements

We thank J. Aarts, T.-M. Chuang, J. C. Davis, M. H. Hamidian, T. van Klingeren, J. Lee, M. Leeuwenhoek, V. Madhavan, F. M. Massee, K. van Oosten, J. van Ruitenbeek, S. Tewari, G. Verdoes and J. J. T. Wagenaar for valuable discussions. We acknowledge funding from the Netherlands Organization for Scientific Research (NOW/OCW) as part of the Frontiers of Nanoscience programme and the Vidi talent scheme, and from the Swiss National Science Foundation (200021-146995).

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Author notes

  1. I. Battisti and K. M. Bastiaans: These authors contributed equally to this work.

Authors and Affiliations

  1. Leiden Institute of Physics, Leiden University, Niels Bohrweg 2, 2333 CA Leiden, The Netherlands

    I. Battisti, K. M. Bastiaans, V. Fedoseev, N. Iliopoulos, J. Zaanen & M. P. Allan

  2. Department of Quantum Matter Physics, University of Geneva, 24 Quai Ernest-Ansermet, 1211 Geneva 4, Switzerland

    A. de la Torre, A. Tamai & F. Baumberger

  3. Department of Physics, California Institute of Technology, Pasadena, California 91125, USA

    A. de la Torre

  4. School of Physics and Astronomy, The University of Edinburgh, James Clerk Maxwell Building, Mayfield Road, Edinburgh EH9 2TT, UK

    E. C. Hunter

  5. London Centre for Nanotechnology and UCL Centre for Materials Discovery, University College London, London WC1E 6BT, UK

    R. S. Perry

  6. Swiss Light Source, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland

    F. Baumberger

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Contributions

I.B., K.M.B., V.F. and M.P.A. performed spectroscopic-imaging STM experiments and analysed data, E.C.H., A.d.l.T. and R.S.P. created and characterized the samples, M.P.A. supervised the study. All authors contributed to the interpretation of the data.

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Correspondence to M. P. Allan.

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Battisti, I., Bastiaans, K., Fedoseev, V. et al. Universality of pseudogap and emergent order in lightly doped Mott insulators. Nature Phys 13, 21–25 (2017). https://doi.org/10.1038/nphys3894

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