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Published January 2017 | Supplemental Material + Submitted
Journal Article Open

Universality of pseudogap and emergent order in lightly doped Mott insulators

Abstract

It is widely believed that high-temperature superconductivity in the cuprates emerges from doped Mott insulators. 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 (Sr_(1−x)La_x)_2IrO_4, which is an effective spin-1/2 Mott insulator like the cuprates, but is chemically radically different. 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 cuprates. 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.

Additional Information

© 2016 Macmillan Publishers Limited. Received 2 June 2016; accepted 24 August 2016; published online 19 September 2016. 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). Data availability: The data that support the plots within this paper and other findings of this study are available from the corresponding author upon reasonable request. These authors contributed equally to this work: I. Battisti & K. M. Bastiaans Author 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. The authors declare no competing financial interests.

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Submitted - 1604.08343.pdf

Supplemental Material - nphys3894-s1.pdf

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August 19, 2023
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