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Quantum spin nematic phase in a square-lattice iridate.

Authors
  • Kim, Hoon1, 2
  • Kim, Jin-Kwang1, 2
  • Kwon, Junyoung2
  • Kim, Jimin1, 2
  • Kim, Hyun-Woo J1, 2
  • Ha, Seunghyeok1, 2
  • Kim, Kwangrae1, 2
  • Lee, Wonjun1, 2
  • Kim, Jonghwan3, 4
  • Cho, Gil Young1, 2
  • Heo, Hyeokjun5
  • Jang, Joonho5
  • Sahle, C J6
  • Longo, A6, 7
  • Strempfer, J8
  • Fabbris, G8
  • Choi, Y8
  • Haskel, D8
  • Kim, Jungho8
  • Kim, J -W8
  • And 1 more
  • 1 Center for Artificial Low Dimensional Electronic Systems, Institute for Basic Science, Pohang, South Korea. , (North Korea)
  • 2 Department of Physics, Pohang University of Science and Technology, Pohang, South Korea. , (North Korea)
  • 3 Center for Van der Waals Quantum Solids, Institute for Basic Science, Pohang, Korea. , (North Korea)
  • 4 Department of Materials Science and Engineering, Pohang University of Science and Technology, Pohang, Korea. , (North Korea)
  • 5 Department of Physics and Astronomy, Seoul National University, Seoul, South Korea. , (North Korea)
  • 6 ESRF, The European Synchrotron, Grenoble, France. , (France)
  • 7 Istituto per lo Studio dei Materiali Nanostrutturati (ISMN)-CNR, UOS Palermo, Palermo, Italy. , (Italy)
  • 8 Advanced Photon Source, Argonne National Laboratory, Argonne, IL, USA.
  • 9 Center for Artificial Low Dimensional Electronic Systems, Institute for Basic Science, Pohang, South Korea. [email protected]. , (North Korea)
  • 10 Department of Physics, Pohang University of Science and Technology, Pohang, South Korea. [email protected]. , (North Korea)
Type
Published Article
Journal
Nature
Publisher
Springer Nature
Publication Date
Dec 13, 2023
Identifiers
DOI: 10.1038/s41586-023-06829-4
PMID: 38093009
Source
Medline
Language
English
License
Unknown

Abstract

Spin nematic is a magnetic analogue of classical liquid crystals, a fourth state of matter exhibiting characteristics of both liquid and solid1,2. Particularly intriguing is a valence-bond spin nematic3-5, in which spins are quantum entangled to form a multipolar order without breaking time-reversal symmetry, but its unambiguous experimental realization remains elusive. Here we establish a spin nematic phase in the square-lattice iridate Sr2IrO4, which approximately realizes a pseudospin one-half Heisenberg antiferromagnet in the strong spin-orbit coupling limit6-9. Upon cooling, the transition into the spin nematic phase at TC ≈ 263 K is marked by a divergence in the static spin quadrupole susceptibility extracted from our Raman spectra and concomitant emergence of a collective mode associated with the spontaneous breaking of rotational symmetries. The quadrupolar order persists in the antiferromagnetic phase below TN ≈ 230 K and becomes directly observable through its interference with the antiferromagnetic order in resonant X-ray diffraction, which allows us to uniquely determine its spatial structure. Further, we find using resonant inelastic X-ray scattering a complete breakdown of coherent magnon excitations at short-wavelength scales, suggesting a many-body quantum entanglement in the antiferromagnetic state10,11. Taken together, our results reveal a quantum order underlying the Néel antiferromagnet that is widely believed to be intimately connected to the mechanism of high-temperature superconductivity12,13. © 2023. The Author(s), under exclusive licence to Springer Nature Limited.

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