Fujihala Masayoshi, Morita Katsuhiro, Mole Richard, Mitsuda Setsuo, Tohyama Takami, Yano Shin-Ichiro, Yu Dehong, Sota Shigetoshi, Kuwai Tomohiko, Koda Akihiro, Okabe Hirotaka, Lee Hua, Itoh Shinichi, Hawai Takafumi, Masuda Takatsugu, Sagayama Hajime, Matsuo Akira, Kindo Koichi, Ohira-Kawamura Seiko, Nakajima Kenji
Tokyo University of Science, Department of Physics, Tokyo, 162-8601, Japan.
Tokyo University of Science, Department of Applied Physics, Tokyo, 125-8585, Japan.
Nat Commun. 2020 Jul 9;11(1):3429. doi: 10.1038/s41467-020-17235-z.
Observation of a quantum spin liquid (QSL) state is one of the most important goals in condensed-matter physics, as well as the development of new spintronic devices that support next-generation industries. The QSL in two dimensional quantum spin systems is expected to be due to geometrical magnetic frustration, and thus a kagome-based lattice is the most probable playground for QSL. Here, we report the first experimental results of the QSL state on a square-kagome quantum antiferromagnet, KCuAlBiO(SO)Cl. Comprehensive experimental studies via magnetic susceptibility, magnetisation, heat capacity, muon spin relaxation (μSR), and inelastic neutron scattering (INS) measurements reveal the formation of a gapless QSL at very low temperatures close to the ground state. The QSL behavior cannot be explained fully by a frustrated Heisenberg model with nearest-neighbor exchange interactions, providing a theoretical challenge to unveil the nature of the QSL state.
观测量子自旋液体（QSL）态是凝聚态物理领域最重要的目标之一，同时对于支持下一代产业的新型自旋电子器件的发展也至关重要。二维量子自旋系统中的QSL预计源于几何磁阻挫，因此基于 Kagome 的晶格是QSL最有可能出现的体系。在此，我们报道了在正方 Kagome 量子反铁磁体 KCuAlBiO(SO)Cl 上关于QSL态的首个实验结果。通过磁化率、磁化强度、热容量、μ子自旋弛豫（μSR）和非弹性中子散射（INS）测量进行的全面实验研究表明，在非常接近基态的低温下形成了无隙QSL。具有最近邻交换相互作用的阻挫海森堡模型无法完全解释QSL行为，这为揭示QSL态的本质带来了理论挑战。
