Nematic transitions in iron pnictide superconductors imaged with a quantum gas

Abstract

The Scanning Quantum Cryogenic Atom Microscope (SQCRAMscope) uses an atomic Bose–Einstein condensate to measure magnetic fields emanating from solid-state samples. The quantum sensor does so with unprecedented d.c. sensitivity at micrometre resolution, from room to cryogenic temperatures1. An additional advantage of the SQCRAMscope is the preservation of optical access to the sample so that magnetometry imaging of, for example, electron transport may be performed in concert with other imaging techniques. Here, we apply this multimodal imaging capability to the study of nematicity in iron pnictide high-temperature superconductors, where the relationship between electronic and structural symmetry breaking resulting in a nematic phase is under debate2. We combine the SQCRAMscope with an in situ microscope that measures optical birefringence near the surface. This enables simultaneous and spatially resolved detection of both bulk and near-surface manifestations of nematicity via transport and structural deformation channels, respectively. By performing local measurements of emergent resistivity anisotropy in iron pnictides, we observe sharp, nearly concurrent transport and structural transitions. More broadly, these measurements demonstrate the SQCRAMscope’s ability to reveal important insights into the physics of complex quantum materials.

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Fig. 1: Multimodal SQCRAMscope.
Fig. 2: Optical birefringence, magnetometry and transport images.
Fig. 3: Temperature dependence of nematic order.
Fig. 4: Nematic transition temperatures.

Data availability

The data represented in Figs. 2–4 are available as source data 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.

Code availability

The code supporting the figures and other findings of this study is available from the corresponding author upon request.

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Acknowledgements

We thank S. Kivelson for discussions and J.-H. Chu for early samples. We acknowledge funding support for apparatus construction from the US Office of Naval Research (ONR) (N00014-17-1-2248). Funding for F.Y. and partial support for S.D.E. were provided by the US Department of Energy, Office of Science, Office of Basic Energy Sciences, under award no. DE-SC0019174. Crystal growth and sample preparation were supported by the US Department of Energy, Office of Basic Energy Sciences, under contract no. DE-AC02-76SF00515. Fabrication of sample mount substrates and the atom chip were performed at the Stanford Nanofabrication Facility and the Stanford Nano Shared Facility, supported by the NSF under award no. ECCS-1542152. S.D.E. acknowledges partial support from the Karel Urbanek Postdoctoral Fellowship. S.F.T. and B.L.L. acknowledge support from the Gordon and Betty Moore Foundation through grant no. GBMF3502 and from the US Army Research Office (ARO) (W911NF1910392). J.C.P. acknowledges support from an NSF Graduate Research Fellowship (DGE-114747), a Gabilan Stanford Graduate Fellowship and the Gerald J. Lieberman Fellowship.

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Contributions

J.C.P. and I.R.F. fabricated and characterized the samples. F.Y., S.F.T. and S.D.E. performed the experiments, and F.Y., S.F.T., S.D.E. and B.L.L. analysed the data. S.D.E., F.Y., S.F.T. and B.L.L. wrote the manuscript. B.L.L. and I.R.F. conceived the project, and B.L.L. supervised the project.

Corresponding author

Correspondence to Benjamin L. Lev.

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The authors declare no competing interests.

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

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Supplementary information

Source data

Source Data Fig. 2

Representative optical birefringence, magnetometry and transport image data.

Source Data Fig. 3

Temperature dependence of nematic order in a wide temperature range.

Source Data Fig. 4

Temperature dependence of nematic order near the nematic phase transition.

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Yang, F., Taylor, S.F., Edkins, S.D. et al. Nematic transitions in iron pnictide superconductors imaged with a quantum gas. Nat. Phys. 16, 514–519 (2020). https://doi.org/10.1038/s41567-020-0826-8

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