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Nematicity and nematic fluctuations in iron-based superconductors

Abstract

The spontaneous reduction of rotational symmetry in a crystalline solid driven by an electronic mechanism is referred to as electronic nematicity. This phenomenon—initially thought to be rare—has now been observed in an increasing number of strongly interacting systems. In particular, the ubiquitous presence of nematicity in a number of unconventional superconductors suggests its importance in developing a unified understanding of their intricate phase diagrams and superconducting pairing. In this regard, the iron-based superconductors present an ideal material platform to study electronic nematicity. Their nematic transition is pronounced, it can be studied with a wide range of experimental techniques, it is easily tunable, and high-quality samples are widely available. Signatures of nematic quantum criticality near optimal dopings have been reported in almost all families of iron-based superconductors. Here we highlight how the nematic phase in this class of materials can be addressed in its full complexity, encompassing momentum-, time-, energy- and material-dependences. We also discuss a number of important open questions that pertain to how nematicity affects the superconducting pairing and normal-state properties, and intriguing quantum-critical behaviour near the nematic transition.

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Fig. 1: Schematic of nematicity manifested in iron-pnictide superconductors.
Fig. 2: Signatures of nematicity in experimental probes.
Fig. 3: Nematic susceptibility and material diversity.

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Acknowledgements

We would like to thank I. Fisher and Q. Si for valuable comments and A. Kreyssig for critical and helpful reading of this manuscript. A.E.B. acknowledges support from the German Research Foundation (DFG) under CRC/TRR 288 (Project A02) and from the Helmholtz Association under contract no. VH-NG-1242. J.H.C. acknowledges the support of the Gordon and Betty Moore Foundation’s EPiQS Initiative, grant no. GBMF6759 to J.-H.C., the David and Lucile Packard Foundation, and the US Air Force Office of Scientific Research under grant no. FA9550-21-1-0068. S.L. is supported by the US Department of Energy, Office of Science, National Quantum Information Science Research Centers, Quantum Systems Accelerator (QSA). M.Y. acknowledges support from the US Department of Energy grant no. DE-SC0021421, the Robert A. Welch Foundation grant no. C-2024, and the Gordon and Betty Moore Foundation’s EPiQS Initiative through grant no. GBMF9470.

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Böhmer, A.E., Chu, JH., Lederer, S. et al. Nematicity and nematic fluctuations in iron-based superconductors. Nat. Phys. 18, 1412–1419 (2022). https://doi.org/10.1038/s41567-022-01833-3

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