Evidence for a cos (4φ) modulation of the superconducting energy gap of optimally doped FeTe0.6Se0.4 single crystals using laser angle-resolved photoemission spectroscopy

K. Okazaki; Y. Ito; Y. Ota; Y. Kotani; T. Shimojima; T. Kiss; S. Watanabe; C. T. Chen; S. Niitaka; T. Hanaguri; H. Takagi; A. Chainani; S. Shin

doi:10.1103/PhysRevLett.109.237011

Evidence for a cos (4φ) modulation of the superconducting energy gap of optimally doped FeTe_0.6Se_0.4 single crystals using laser angle-resolved photoemission spectroscopy

K. Okazaki, Y. Ito, Y. Ota, Y. Kotani, T. Shimojima, T. Kiss, S. Watanabe, C. T. Chen, S. Niitaka, T. Hanaguri, H. Takagi, A. Chainani, S. Shin

Department of Physics

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Abstract

We study the superconducting-gap anisotropy of the Γ-centered hole Fermi surface in optimally doped FeTe_0.6Se_0.4 (T _c=14.5 K), using laser-excited angle-resolved photoemission spectroscopy. We observe sharp superconducting (SC) coherence peaks at T=2.5 K. In contrast to earlier angle-resolved photoemission spectroscopy studies but consistent with thermodynamic results, the momentum dependence shows a cos (4φ) modulation of the SC-gap anisotropy. The observed SC-gap anisotropy strongly indicates that the pairing interaction is not a conventional phonon-mediated isotropic one. Instead, the results suggest the importance of second-nearest-neighbor electronic interactions between the iron sites in the framework of s_±-wave superconductivity.

Original language	English
Article number	237011
Journal	Physical review letters
Volume	109
Issue number	23
DOIs	https://doi.org/10.1103/PhysRevLett.109.237011
Publication status	Published - 2012 Dec 6

All Science Journal Classification (ASJC) codes

Physics and Astronomy(all)

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10.1103/PhysRevLett.109.237011

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Okazaki, K., Ito, Y., Ota, Y., Kotani, Y., Shimojima, T., Kiss, T., Watanabe, S., Chen, C. T., Niitaka, S., Hanaguri, T., Takagi, H., Chainani, A., & Shin, S. (2012). Evidence for a cos (4φ) modulation of the superconducting energy gap of optimally doped FeTe_0.6Se_0.4 single crystals using laser angle-resolved photoemission spectroscopy. Physical review letters, 109(23), [237011]. https://doi.org/10.1103/PhysRevLett.109.237011

Okazaki, K. ; Ito, Y. ; Ota, Y. ; Kotani, Y. ; Shimojima, T. ; Kiss, T. ; Watanabe, S. ; Chen, C. T. ; Niitaka, S. ; Hanaguri, T. ; Takagi, H. ; Chainani, A. ; Shin, S. / Evidence for a cos (4φ) modulation of the superconducting energy gap of optimally doped FeTe_0.6Se_0.4 single crystals using laser angle-resolved photoemission spectroscopy. In: Physical review letters. 2012 ; Vol. 109, No. 23.

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title = "Evidence for a cos (4φ) modulation of the superconducting energy gap of optimally doped FeTe0.6Se0.4 single crystals using laser angle-resolved photoemission spectroscopy",

abstract = "We study the superconducting-gap anisotropy of the Γ-centered hole Fermi surface in optimally doped FeTe0.6Se0.4 (T c=14.5 K), using laser-excited angle-resolved photoemission spectroscopy. We observe sharp superconducting (SC) coherence peaks at T=2.5 K. In contrast to earlier angle-resolved photoemission spectroscopy studies but consistent with thermodynamic results, the momentum dependence shows a cos (4φ) modulation of the SC-gap anisotropy. The observed SC-gap anisotropy strongly indicates that the pairing interaction is not a conventional phonon-mediated isotropic one. Instead, the results suggest the importance of second-nearest-neighbor electronic interactions between the iron sites in the framework of s±-wave superconductivity.",

author = "K. Okazaki and Y. Ito and Y. Ota and Y. Kotani and T. Shimojima and T. Kiss and S. Watanabe and Chen, {C. T.} and S. Niitaka and T. Hanaguri and H. Takagi and A. Chainani and S. Shin",

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doi = "10.1103/PhysRevLett.109.237011",

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Okazaki, K, Ito, Y, Ota, Y, Kotani, Y, Shimojima, T, Kiss, T, Watanabe, S, Chen, CT, Niitaka, S, Hanaguri, T, Takagi, H, Chainani, A & Shin, S 2012, 'Evidence for a cos (4φ) modulation of the superconducting energy gap of optimally doped FeTe_0.6Se_0.4 single crystals using laser angle-resolved photoemission spectroscopy', Physical review letters, vol. 109, no. 23, 237011. https://doi.org/10.1103/PhysRevLett.109.237011

Evidence for a cos (4φ) modulation of the superconducting energy gap of optimally doped FeTe_0.6Se_0.4 single crystals using laser angle-resolved photoemission spectroscopy. / Okazaki, K.; Ito, Y.; Ota, Y.; Kotani, Y.; Shimojima, T.; Kiss, T.; Watanabe, S.; Chen, C. T.; Niitaka, S.; Hanaguri, T.; Takagi, H.; Chainani, A.; Shin, S.

In: Physical review letters, Vol. 109, No. 23, 237011, 06.12.2012.

Research output: Contribution to journal › Article › peer-review

TY - JOUR

T1 - Evidence for a cos (4φ) modulation of the superconducting energy gap of optimally doped FeTe0.6Se0.4 single crystals using laser angle-resolved photoemission spectroscopy

AU - Okazaki, K.

AU - Ito, Y.

AU - Ota, Y.

AU - Kotani, Y.

AU - Shimojima, T.

AU - Kiss, T.

AU - Watanabe, S.

AU - Chen, C. T.

AU - Niitaka, S.

AU - Hanaguri, T.

AU - Takagi, H.

AU - Chainani, A.

AU - Shin, S.

PY - 2012/12/6

Y1 - 2012/12/6

N2 - We study the superconducting-gap anisotropy of the Γ-centered hole Fermi surface in optimally doped FeTe0.6Se0.4 (T c=14.5 K), using laser-excited angle-resolved photoemission spectroscopy. We observe sharp superconducting (SC) coherence peaks at T=2.5 K. In contrast to earlier angle-resolved photoemission spectroscopy studies but consistent with thermodynamic results, the momentum dependence shows a cos (4φ) modulation of the SC-gap anisotropy. The observed SC-gap anisotropy strongly indicates that the pairing interaction is not a conventional phonon-mediated isotropic one. Instead, the results suggest the importance of second-nearest-neighbor electronic interactions between the iron sites in the framework of s±-wave superconductivity.

AB - We study the superconducting-gap anisotropy of the Γ-centered hole Fermi surface in optimally doped FeTe0.6Se0.4 (T c=14.5 K), using laser-excited angle-resolved photoemission spectroscopy. We observe sharp superconducting (SC) coherence peaks at T=2.5 K. In contrast to earlier angle-resolved photoemission spectroscopy studies but consistent with thermodynamic results, the momentum dependence shows a cos (4φ) modulation of the SC-gap anisotropy. The observed SC-gap anisotropy strongly indicates that the pairing interaction is not a conventional phonon-mediated isotropic one. Instead, the results suggest the importance of second-nearest-neighbor electronic interactions between the iron sites in the framework of s±-wave superconductivity.

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Evidence for a cos (4φ) modulation of the superconducting energy gap of optimally doped FeTe_0.6Se_0.4 single crystals using laser angle-resolved photoemission spectroscopy

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