Quantum spin nematic phase in a square-lattice iridate

• 成果类型: Article
• 署名作者: Kim, Hoon; Kim, Jin-Kwang; Kwon, Junyoung; Kim, Jimin; Kim, Hyun-Woo J.; Ha, Seunghyeok; Kim, Kwangrae; Lee, Wonjun; Kim, Jonghwan; Cho, Gil Young; Heo, Hyeokjun; Jang, Joonho; Sahle, C. J.; Longo, A.; Strempfer, J.; Fabbris, G.; Choi, Y.; Haskel, D.; Kim, Jungho; Kim, J. -w.; Kim, B. J.
• 署名单位: Institute for Basic Science - Korea (IBS); Pohang University of Science & Technology (POSTECH); Institute for Basic Science - Korea (IBS); Pohang University of Science & Technology (POSTECH); Seoul National University (SNU); European Synchrotron Radiation Facility (ESRF); Consiglio Nazionale delle Ricerche (CNR); Istituto per lo Studio dei Materiali Nanostrutturati (ISMN-CNR); United States Department of Energy (DOE); Argonne National Laboratory
• 刊物名称: Nature
• ISSN/ISSBN: 0028-6646
• DOI: 10.1038/s41586-023-06829-4
• 发表日期: 2024-01-11
• 页码: 264-269
• 关键词: dynamics; la2cuo4; state

摘要

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 approximate to 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 approximate to 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 Neel antiferromagnet that is widely believed to be intimately connected to the mechanism of high-temperature superconductivity12,13. We establish a spin nematic phase in the square-lattice iridate Sr2IrO4 and find a complete breakdown of coherent magnon excitations at short-wavelength scales, suggesting a many-body quantum entanglement in the antiferromagnetic state.