2023-12-14 韓国基礎科学研究院(IBS)
◆スピン・ネマティック位相の発見は、量子コンピューティングや情報技術に影響を与え、また高温超伝導への可能性も示唆されている。キム・ボムジュン教授は、韓国のX線実験の進展によりこの研究が可能になったと述べ、P.W.アンダーソンの提案に基づく高温超伝導の重要性も強調されている。
＜関連情報＞
- https://www.ibs.re.kr/cop/bbs/BBSMSTR_000000000738/selectBoardArticle.do
- https://www.nature.com/articles/s41586-023-06829-4
正方格子イリジウムの量子スピンネマチック位相 Quantum spin nematic phase in a square-lattice iridate
Hoon Kim,Jin-Kwang Kim,Junyoung Kwon,Jimin Kim,Hyun-Woo J. Kim,Seunghyeok Ha,Kwangrae Kim,Wonjun Lee,Jonghwan Kim,Gil Young Cho,Hyeokjun Heo,Joonho Jang,C. J. Sahle,A. Longo,J. Strempfer,G. Fabbris,Y. Choi,D. Haskel,Jungho Kim,J. -W. Kim & B. J. Kim
Nature Published:13 December 2023
DOI:https://doi.org/10.1038/s41586-023-06829-4
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 nematic3,4,5, 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 limit6,7,8,9. 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.
