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Superconductivity and quantum criticality linked by the Hall effect in a strange metal


Many unconventional superconductors exhibit a common set of anomalous charge transport properties that characterize them as ‘strange metals’, which provides hope that there is a single theory that describes them1,2,3. However, model-independent connections between the strange metals and superconductivity have remained elusive. Here, we show that the Hall effect of the unconventional superconductor BaFe2(As1−xPx)2 contains an anomalous contribution arising from the correlations within the strange metal. This term has a distinctive dependence on the magnetic field, which allows us to track its behaviour across the doping–temperature phase diagram, even under the superconducting dome. These measurements demonstrate that the strange metal Hall component emanates from a quantum critical point and, in the zero-temperature limit, decays together with the superconducting critical temperature. This empirically reveals the structure of the connection between superconductivity and quantum criticality, which may be common to the physics of many strange metal superconductors.

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Fig. 1: Strange metal behaviour in BaFe2(As1−xPx)2.
Fig. 2: Low-temperature Hall coefficient of BaFe2(As1−xPx)2.
Fig. 3: Low-field enhancement of the Hall number across the critical fan.

Data availability

Source data are available for this paper. All other data that support the plots within this paper and other findings of this study are available from the corresponding author on reasonable request.


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We thank D.-H. Lee and C. Varma for fruitful discussions. This work is supported by the Gordon and Betty Moore Foundation’s EPiQS Initiative through grant number GBMF9067. Materials synthesis by N.M. was performed as part of the Quantum Materials programme supported by the Director, Office of Science, Office of Basic Energy Sciences, Materials Sciences and Engineering Division of the US Department of Energy under contract number DE-AC02-05CH11231. A portion work was performed at the National High Magnetic Field Laboratory, which is supported by National Science Foundation Cooperative Agreement Numbers DMR-1157490 and DMR-1644779 and the State of Florida. B.J.R., M.K.C. and R.D.M. acknowledge funding from the US Department of Energy Office of Basic Energy Sciences Science under the 100 T programme.

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Authors and Affiliations



I.M.H. and J.G.A. conceived the project. I.M.H. and N.M. synthesized the samples. I.M.H., N.M., M.K.C., G.N.L., B.J.R. and R.D.M. performed the measurements. I.M.H. and J.G.A. analysed the data and wrote the manuscript with input from all of the authors.

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Correspondence to James G. Analytis.

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The authors declare no competing interests.

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Peer review information Nature Physics thanks Nigel Hussey and Andrew Schofield for their contribution to the peer review of this work.

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Supplementary information

Supplementary Information

Supplementary Figs. 1 and 2 and discussion sections I and II.

Source data

Source Data Fig. 1

Hall coefficient numerical values plotted in Fig. 1.

Source Data Fig. 2

Hall coefficient numerical values plotted in Fig. 2.

Source Data Fig. 3

Hall coefficient numerical values plotted in Fig. 3.

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Hayes, I.M., Maksimovic, N., Lopez, G.N. et al. Superconductivity and quantum criticality linked by the Hall effect in a strange metal. Nat. Phys. 17, 58–62 (2021).

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