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Preferred Spin Excitations in the Bilayer Iron-Based Superconductor CaK(Fe0.96Ni0.04)4As4 with Spin-Vortex Crystal Order

Chang Liu, Philippe Bourges, Yvan Sidis, Tao Xie, Guanghong He, Frédéric Bourdarot, Sergey Danilkin, Haranath Ghosh, Soumyadeep Ghosh, Xiaoyan Ma, Shiliang Li, Yuan Li, and Huiqian Luo
Phys. Rev. Lett. 128, 137003 – Published 31 March 2022
Physics logo See synopsis: Spin Fluctuations May Drive Iron-Based Superconductivity
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Abstract

Spin-orbit coupling (SOC) is a key to understand the magnetically driven superconductivity in iron-based superconductors, where both local and itinerant electrons are present and the orbital angular momentum is not completely quenched. Here, we report a neutron scattering study on the bilayer compound CaK(Fe0.96Ni0.04)4As4 with superconductivity coexisting with a noncollinear spin-vortex crystal magnetic order that preserves the tetragonal symmetry of the Fe-Fe plane. In the superconducting state, two spin resonance modes with odd and even L symmetries due to the bilayer coupling are found similar to the undoped compound CaKFe4As4 but at lower energies. Polarization analysis reveals that the odd mode is c-axis polarized, and the low-energy spin anisotropy can persist to the paramagnetic phase at high temperature, which closely resembles other systems with in-plane collinear and c-axis biaxial magnetic orders. These results provide the missing piece of the puzzle on the SOC effect in iron-pnictide superconductors, and also establish a common picture of c-axis preferred magnetic excitations below Tc regardless of the details of magnetic pattern or lattice symmetry.

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  • Received 10 January 2022
  • Accepted 23 February 2022

DOI:https://doi.org/10.1103/PhysRevLett.128.137003

© 2022 American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied Physics

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Spin Fluctuations May Drive Iron-Based Superconductivity

Published 31 March 2022

An experiment finds that spin fluctuations in an iron-based superconductor have a preferred direction, suggesting a potential mechanism for superconductivity in these materials.

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Authors & Affiliations

Chang Liu1,2, Philippe Bourges3,*, Yvan Sidis3, Tao Xie4, Guanghong He5, Frédéric Bourdarot6, Sergey Danilkin7, Haranath Ghosh8,9, Soumyadeep Ghosh8,9, Xiaoyan Ma1,2, Shiliang Li1,2,10, Yuan Li5,11,†, and Huiqian Luo1,10,‡

  • 1Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
  • 2School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190, China
  • 3Laboratoire Léon Brillouin, CEA-CNRS, Université Paris-Saclay, CEA Saclay, 91191 Gif-sur-Yvette, France
  • 4Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
  • 5International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
  • 6Université Grenoble Alpes, CEA, INAC, MEM MDN, F-38000 Grenoble, France
  • 7Australian Centre for Neutron Scattering, Australian Nuclear Science and Technology Organization, Lucas Heights NSW-2234, Australia
  • 8Human Resources Development Section, Raja Ramanna Centre for Advanced Technology, Indore 452013, India
  • 9Homi Bhabha National Institute, BARC training school complex 2nd floor, Anushakti Nagar, Mumbai 400094, India
  • 10Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808, China
  • 11Collaborative Innovation Center of Quantum Matter, Beijing 100871, China

  • *philippe.bourges@cea.fr
  • yuan.li@pku.edu.cn
  • hqluo@iphy.ac.cn

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Issue

Vol. 128, Iss. 13 — 1 April 2022

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