Skip to main content

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

  • Article
  • Published:

Carrier density crossover and quasiparticle mass enhancement in a doped 5d Mott insulator

Nature Physics volume 20, pages 1596–1602 (2024)Cite this article

Subjects

Abstract

High-temperature superconductivity in cuprates emerges upon doping the parent Mott insulator. Key features of the low-doped cuprate superconductors include an effective carrier density that tracks the number of doped holes, the emergence of an anisotropic pseudogap that is characterized by disconnected Fermi arcs and the closure of the gap at a critical doping level. In Sr2IrO4, a spin–orbit-coupled Mott insulator often regarded as a 5d analogue of the cuprates, surface probes have also revealed the emergence of an anisotropic pseudogap and Fermi arcs under electron doping. However, neither the corresponding critical doping nor the bulk signatures of pseudogap closure have yet been observed. Here we demonstrate that electron-doped Sr2IrO4 exhibits a critical doping level with a marked crossover in the effective carrier density at low temperatures. This is accompanied by a five-orders-of-magnitude increase in conductivity and a sixfold enhancement in the electronic specific heat. These collective findings resemble the bulk pseudogap phenomenology in cuprates. However, given that electron-doped Sr2IrO4 is non-superconducting, it suggests that the pseudogap may not be a state of precursor pairing. Therefore, our results narrow the search for the key ingredient underpinning the formation of the superconducting condensate in doped Mott insulators.

This is a preview of subscription content, access via your institution

Access options

Buy this article

  • Purchase on SpringerLink
  • Instant access to full article PDF
Buy now

Prices may be subject to local taxes which are calculated during checkout

Fig. 1: Hall effect in Sr2−xLaxIrO4.
Fig. 2: Longitudinal resistivity and mobility of Sr2−xLaxIrO4.
Fig. 3: Low-temperature specific heat of Sr2−xLaxIrO4.
Fig. 4: Doping evolution of the Hall number and specific heat in the T = 0 limit.

Similar content being viewed by others

Data availability

Source data are provided with this paper and available from the Dryad data repository (https://doi.org/10.5061/dryad.79cnp5j4h)55. Any additional data are available from the corresponding authors upon request.

Code availability

The codes associated with the band structure and transport coefficient calculations that support this study are available from the corresponding authors upon request.

References

  1. Imada, M. Two types of Mott transitions. J. Phys. Soc. Jpn 62, 1105–1108 (1993).

    ADS  Google Scholar 

  2. Tokura, Y. et al. Filling dependence of electronic properties on the verge of metal–Mott-insulator transition in Sr1−xLaxTiO3. Phys. Rev. Lett. 70, 2126–2129 (1993).

    ADS  Google Scholar 

  3. Ando, Y., Kurita, Y., Komiya, S., Ono, S. & Segawa, K. Evolution of the Hall coefficient and the peculiar electronic structure of the cuprate superconductors. Phys. Rev. Lett. 92, 197001 (2004).

    ADS  Google Scholar 

  4. Padilla, W. J. et al. Constant effective mass across the phase diagram of high-Tc cuprates. Phys. Rev. B 72, 060511 (2005).

    ADS  Google Scholar 

  5. Norman, M. R. et al. Destruction of the Fermi surface in underdoped high-Tc superconductors. Nature 392, 157–160 (1998).

    ADS  Google Scholar 

  6. Alloul, H., Ohno, T. & Mendels, P. 89Y NMR evidence for a Fermi-liquid behavior in YBa2Cu3O6+x. Phys. Rev. Lett. 63, 1700–1703 (1989).

    ADS  Google Scholar 

  7. 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).

    ADS  Google Scholar 

  8. Tallon, J. L., Storey, J., Cooper, J. R. & Loram, J. W. Locating the pseudogap closing point in cuprate superconductors: absence of entrant or reentrant behavior. Phys. Rev. B 101, 174512 (2018).

    ADS  Google Scholar 

  9. Emery, V. J. & Kivelson, S. A. Importance of phase fluctuations in superconductors with small superfluid density. Nature 374, 434–437 (1995).

    ADS  Google Scholar 

  10. Zhou, P. et al. Electron pairing in the pseudogap state revealed by shot noise in copper oxide junctions. Nature 572, 493–496 (2019).

    ADS  Google Scholar 

  11. Park, H., Haule, K. & Kotliar, G. Cluster dynamical mean field theory of the Mott transition. Phys. Rev. Lett. 101, 186403 (2008).

    ADS  Google Scholar 

  12. Rubtsov, A. N., Katsnelson, M. I. & Lichtenstein, A. I. Dual fermion approach to nonlocal correlations in the Hubbard model. Phys. Rev. B 77, 033101 (2008).

    ADS  Google Scholar 

  13. Badoux, S. et al. Change of carrier density at the pseudogap critical point of a cuprate superconductor. Nature 531, 210–214 (2016).

    ADS  Google Scholar 

  14. Collignon, C. et al. Fermi-surface transformation across the pseudogap critical point of the cuprate superconductor La1.6−xNd0.4SrxCuO4. Phys. Rev. B 95, 224517 (2017).

    ADS  Google Scholar 

  15. Michon, B. et al. Thermodynamic signatures of quantum criticality in cuprate superconductors. Nature 567, 218–222 (2019).

    ADS  Google Scholar 

  16. Hussey, N. E., Buhot, J. & Licciardello, S. A tale of two metals: contrasting criticalities in the pnictides and hole-doped cuprates. Rep. Prog. Phys. 81, 052501 (2018).

    MathSciNet  ADS  Google Scholar 

  17. Bertinshaw, J., Kim, Y. K., Khaliullin, G. & Kim, B. J. Square lattice iridates. Annu. Rev. Condens. Matter Phys. 10, 315–336 (2019).

    ADS  Google Scholar 

  18. Chen, X. et al. Influence of electron doping on the ground state of (Sr1−xLax)2IrO4. Phys. Rev. B 92, 075215 (2015).

    MathSciNet  Google Scholar 

  19. Gretarsson, H. et al. Persistent paramagnons deep in the metallic phase of Sr2−xLaxIrO4. Phys. Rev. Lett. 117, 107001 (2016).

    ADS  Google Scholar 

  20. Pincini, D. et al. Anisotropic exchange and spin-wave damping in pure and electron-doped Sr2IrO4. Phys. Rev. B 96, 075162 (2017).

    ADS  Google Scholar 

  21. Horigane, K. et al. Magnetic phase diagram of Sr2−xLaxIrO4 synthesized by mechanical alloying. Phys. Rev. B 7, 064425 (2018).

    ADS  Google Scholar 

  22. Rodan, S. T. et al. Quantum critical nature of the short-range magnetic order in Sr2−xLaxIrO4. Phys. Rev. B 98, 214412 (2018).

    ADS  Google Scholar 

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

    ADS  Google Scholar 

  24. 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).

    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).

    ADS  Google Scholar 

  26. Battisti, I. et al. Universality of pseudogap and emergent order in lightly doped Mott insulators. Nat. Phys. 13, 21–25 (2017).

    Google Scholar 

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

    ADS  Google Scholar 

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

    ADS  Google Scholar 

  29. Meng, Z. Y., Kim, Y. B. & Kee, H.-Y. Odd-parity triplet superconducting phase in multiorbital materials with a strong spin–orbit coupling: application to doped Sr2IrO4. Phys. Rev. Lett. 113, 177003 (2014).

    ADS  Google Scholar 

  30. Carter, S. A. et al. Mechanism for the metal–insulator transition in Sr2Ir1��xRuxO4. Phys. Rev. B 51, 17184 (1995).

    ADS  Google Scholar 

  31. Kini, N. S., Strydom, A. M., Jeevan, H. S., Geibel, C. & Ramakrishnan, S. Transport and thermal properties of weakly ferromagnetic Sr2IrO4. J. Phys. Condens. Matter 18, 8205–8216 (2006).

    ADS  Google Scholar 

  32. Mackenzie, A. P. et al. Calculation of thermodynamic and transport properties of Sr2RuO4 at low temperatures using known fermi surface parameters. Phys. C. 263, 510–515 (1996).

    ADS  Google Scholar 

  33. Löhneysen, H., Rosch, A., Vojta, M. & Woelfle, P. Fermi-liquid instabilities at magnetic quantum phase transitions. Rev. Mod. Phys. 79, 1015 (2007).

    ADS  Google Scholar 

  34. Laliberté, F. et al. Origin of the metal-to-insulator crossover in cuprate superconductors. Preprint at https://arxiv.org/abs/1606.04491 (2016).

  35. Putzke, C. et al. Reduced Hall carrier density in the overdoped strange metal regime of cuprate superconductor. Nat. Phys. 17, 826–831 (2021).

    Google Scholar 

  36. Brouet, V. et al. Transfer of spectral weight across the gap of Sr2IrO4 induced by La doping. Phys. Rev. B 92, 081117(R) (2015).

    ADS  Google Scholar 

  37. Ma, Q. et al. Magnetic field tuning of parallel spin stripe order and fluctuations near the pseudogap quantum critical point in La1.36Nd0.4Sr0.24CuO4. Phys. Rev. B 106, 214427 (2022).

    ADS  Google Scholar 

  38. Peng, S. et al. Electronic nature of the pseudogap in electron-doped Sr2IrO4. npj Quantum Mater. 7, 58 (2022).

    ADS  Google Scholar 

  39. Yang, K.-Y., Rice, T. M. & Zhang, F.-C. Phenomenological theory of the pseudogap state. Phys. Rev. B 73, 174501 (2006).

    ADS  Google Scholar 

  40. Chatterjee, S. & Sachdev, S. Fractionalized Fermi liquid with bosonic chargons as a candidate for the pseudogap metal. Phys. Rev. B 94, 205117 (2016).

    ADS  Google Scholar 

  41. Morice, C., Montiel, X. & Pepin, C. Evolution of Hall resistivity and spectral function with doping in the SU(2) theory of cuprates. Phys. Rev. B 96, 134511 (2017).

    ADS  Google Scholar 

  42. Storey, J. G. Hall effect and Fermi surface reconstruction via electron pockets in the high-Tc cuprates. Europhys. Lett. 113, 27003 (2016).

    ADS  Google Scholar 

  43. Verret, S., Simard, O., Charlebois, M., Senechal, D. & Tremblay, A.-M. S. Phenomenological theories of the low-temperature pseudogap: Hall number, specific heat, and Seebeck coefficient. Phys. Rev. B 96, 125139 (2017).

    ADS  Google Scholar 

  44. Moutenet, A., Georges, A. & Ferrero, M. Pseudogap and electronic structure of electron-doped Sr2IrO4. Phys. Rev. B 97, 115109 (2018).

    Google Scholar 

  45. Pelc, D., Popčević, P., Požek, M., Greven, M. & Barišić, N. Unusual behavior of cuprates explained by heterogeneous charge localization. Sci. Adv. 5, eaau4538 (2019).

    ADS  Google Scholar 

  46. Berben, M. et al. Superconducting dome and pseudogap endpoint in Bi2201. Phys. Rev. Mater. 6, 044804 (2022).

    Google Scholar 

  47. Ong, N. P. Geometric interpretation of the weak-field Hall conductivity in two-dimensional metals with arbitrary Fermi surface. Phys. Rev. B 43, 193 (1991).

    ADS  Google Scholar 

  48. Hussey, N. E. The normal state scattering rate of high-Tc cuprates. Eur. Phys. J. B 31, 495–507 (2003).

    ADS  Google Scholar 

  49. Zhong, Y. et al. Differentiated roles of Lifshitz transition on thermodynamics and superconductivity in La2−xSrxCuO4. Proc. Natl Acad. Sci. USA 119, 2204630119 (2022).

    Google Scholar 

  50. Yang, Y. et al. Superconductivity in doped Sr2IrO4: a functional renormalization group study. Phys. Rev. B 89, 094518 (2014).

    ADS  Google Scholar 

  51. Lane, C. et al. First-principles calculation of spin and orbital contributions to magnetically ordered moments in Sr2IrO4. Phys. Rev. B 101, 155110 (2020).

    ADS  Google Scholar 

  52. Watanabe, H., Shirakawa, T. & Yunoki, S. Microscopic study of a spin–orbit-induced Mott insulator in Ir oxides. Phys. Rev. Lett. 105, 216410 (2010).

    ADS  Google Scholar 

  53. Tagliati, S., Krasnov, V. M. & Rydh, A. Differential membrane-based nanocalorimeter for high-resolution measurements of low-temperature specific heat. Rev. Sci. Instrum. 83, 055107 (2012).

    ADS  Google Scholar 

  54. Fortune, N. A. et al. Wide range thin-film ceramic metal-alloy thermometers with low magnetoresistance. Phys. Rev. Appl. 20, 054016 (2023).

    ADS  Google Scholar 

  55. Hsu, Y.-T. et al. Source figure data for research article “Carrier density crossover and quasiparticle mass enhancement in a doped 5d Mott insulator”. Dryad https://doi.org/10.5061/dryad.79cnp5j4h (2024).

Download references

Acknowledgements

We thank F. Baumberger, A. Georges and A. Tamai for fruitful discussions. We would like to thank R. D. H. Hinlopen for assistance with the numerical calculations and G. Stenning and D. Nye for help with the Physical Property Measurement System and Smartlab instruments in the Materials Characterisation Laboratory at the ISIS Neutron and Muon Source. We acknowledge the support of the High Field Magnet Laboratory (Grant No. HFML-RU/NWO-I), a member of the European Magnetic Field Laboratory. This work was supported by the European Research Council under the European Union’s Horizon 2020 research and innovation programme (Grant Agreement No. 835279-Catch-22), by the Swedish Research Council (Grant No. 2021-04360) and by the UK Engineering and Physical Sciences Research Council (Grant Nos. EP/N034694/1 and EP/V02986X/1). Part of this work was also supported by the former Foundation for Fundamental Research on Matter, which is financially supported by the Netherlands Organisation for Scientific Research (Grant No. 16METL01, ‘Strange Metals’).

Author information

Authors and Affiliations

  1. High Field Magnet Laboratory (HFML-FELIX) and Institute for Molecules and Materials, Radboud University, Nijmegen, The Netherlands

    Yu-Te Hsu, Maarten Berben, Caitlin Duffy & Nigel E. Hussey

  2. Department of Physics, National Tsing Hua University, Hsinchu, Taiwan

    Yu-Te Hsu

  3. Department of Physics, Stockholm University, Stockholm, Sweden

    Andreas Rydh

  4. Department of Physics, Northeastern University, Boston, MA, USA

    Alberto de la Torre

  5. London Centre for Nanotechnology and Dept. of Physics and Astronomy, University College London, London, UK

    Robin S. Perry

  6. ISIS Neutron and Muon Source, Rutherford Appleton Laboratory, Harwell, UK

    Robin S. Perry

  7. H. H. Wills Physics Laboratory, University of Bristol, Bristol, UK

    Nigel E. Hussey

Authors
  1. Yu-Te Hsu
    View author publications

    You can also search for this author in PubMed Google Scholar

  2. Andreas Rydh
    View author publications

    You can also search for this author in PubMed Google Scholar

  3. Maarten Berben
    View author publications

    You can also search for this author in PubMed Google Scholar

  4. Caitlin Duffy
    View author publications

    You can also search for this author in PubMed Google Scholar

  5. Alberto de la Torre
    View author publications

    You can also search for this author in PubMed Google Scholar

  6. Robin S. Perry
    View author publications

    You can also search for this author in PubMed Google Scholar

  7. Nigel E. Hussey
    View author publications

    You can also search for this author in PubMed Google Scholar

Contributions

Y.-T.H. designed the project. R.S.P. and A.d.l.T. grew and characterized the crystals. Y.-T.H., M.B. and C.D. performed the magnetotransport measurements. A.R. performed the specific heat measurements. Y.-T.H. performed the numerical calculations. Y.-T.H. and N.E.H. wrote the paper with inputs from all authors.

Corresponding authors

Correspondence to Yu-Te Hsu or Nigel E. Hussey.

Ethics declarations

Competing interests

The authors declare no competing interests.

Peer review

Peer review information

Nature Physics thanks Danfeng Li and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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 Figs. 1–6, Discussion and Tables 1 and 2.

Source data

Source Data Fig. 1

Measured experimental data.

Source Data Fig. 2

Measured experimental data and calculated transport coefficients.

Source Data Fig. 3

Measured experimental data.

Source Data Fig. 4

Calculated transport and thermodynamic coefficients.

Rights and permissions

Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Hsu, YT., Rydh, A., Berben, M. et al. Carrier density crossover and quasiparticle mass enhancement in a doped 5d Mott insulator. Nat. Phys. 20, 1596–1602 (2024). https://doi.org/10.1038/s41567-024-02564-3

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1038/s41567-024-02564-3

Search

Advanced search

Quick links

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