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Sixfold enhancement of superconductivity in a tunable electronic nematic system


The electronic nematic phase—in which electronic degrees of freedom lower the crystal rotational symmetry—is commonly observed in high-temperature superconductors. However, understanding the role of nematicity and nematic fluctuations in Cooper pairing is often made more complicated by the coexistence of other orders, particularly long-range magnetic order. Here we report the enhancement of superconductivity in a model electronic nematic system that is not magnetic, and show that the enhancement is directly born out of strong nematic fluctuations associated with a quantum phase transition. We present measurements of the resistance as a function of strain in Ba1−xSrxNi2As2 to show that strontium substitution promotes an electronically driven nematic order in this system. In addition, the complete suppression of that order to absolute zero temperature leads to an enhancement of the pairing strength, as evidenced by a sixfold increase in the superconducting transition temperature. The direct relation between enhanced pairing and nematic fluctuations in this model system, as well as the interplay with a unidirectional charge-density-wave order comparable to that found in the cuprates, offers a means to investigate the role of nematicity in strengthening superconductivity.

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Fig. 1: Evolution of structural, charge and nematic orders in Ba1−xSrxNi2As2.
Fig. 2: Enhancement of superconducting transition temperature.
Fig. 3: Electronic nematic and charge orders in BaNi2As2.
Fig. 4: Nematic susceptibilities of Ba1−xSrxNi2As2 single crystals.

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Data availability

Source data for Figs. 14 are provided with the paper. All other data that support the plots within this paper and other findings of this study are available from the corresponding author upon reasonable request.


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Research at the University of Maryland was supported by the AFOSR Grant No. FA9550-14-10332, the National Science Foundation Grant No. DMR1905891, and the Gordon and Betty Moore Foundation’s EPiQS Initiative through Grant No. GBMF4419. We also acknowledge support from the Maryland Quantum Materials Center as well as the Maryland Nanocenter and its FabLab. The identification of any commercial product or trade name does not imply endorsement or recommendation by the National Institute of Standards and Technology. Theory work (R.M.F. and M.H.C.) was supported by the US Department of Energy, Office of Science, Basic Energy Sciences under award number DE-SC0012336. X-ray experiments at UIUC were supported by DOE grant DE-FG02-06ER46285. P.A. acknowledges support from the Gordon and Betty Moore Foundation’s EPiQS initiative through grant GBMF4542.

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Authors and Affiliations



C.E. and J.P. conceived and designed the experiments. C.E., D.J.C., T.M., H.H. and T.D. synthesized crystals and performed basic physical characterization. C.E. performed elastoresistivity measurements. J.C., S.L. and P.A. performed and analysed low-temperature X-ray characterization of the CDW phase. P.Z. performed and analysed 250 K single-crystal X-ray diffraction. J.L. performed preliminary neutron diffraction studies. M.H.C. and R.M.F. developed the phenomenological model describing the evolution of nematicity in this system. C.E., J.P., R.M.F. and M.H.C. wrote the manuscript with contributions from all authors.

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Correspondence to Chris Eckberg or Johnpierre Paglione.

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Peer review information Nature Physics thanks Dimitri Basov and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Supplementary information

Supplementary Information

Additional theoretical discussion and experimental data, Supplementary Figs. 1–12 and refs. 1–3.

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Eckberg, C., Campbell, D.J., Metz, T. et al. Sixfold enhancement of superconductivity in a tunable electronic nematic system. Nat. Phys. 16, 346–350 (2020).

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