Quantum spin liquids (QSLs) differ from conventional magnetic materials in that they do not exhibit long-range magnetic order even at absolute zero temperature. Instead, spins in QSLs remain highly entangled, giving rise to topologically protected quantum states. The kagome lattice, a two-dimensional network of edge-sharing triangles, is particularly prone to geometric frustration, which prevents conventional spin alignment and promotes strong quantum fluctuations. These characteristics make kagome spin systems ideal platforms for exploring exotic quantum phases, including quantum spin liquids and field-induced magnetization plateaus.

In this study, the research team successfully observed the 1/9 magnetization plateau in the copper-based kagome compound YCu3(OD)₆+xBr3−x under a strong magnetic field of 15 T. By combining thermodynamic measurements (specific heat, thermal conductivity, and pulsed-field magnetization) with Raman spectroscopy, they identified Dirac spinon quasiparticles, raising the possibility that the plateau state may be linked to an unconventional quantum phase, potentially a Z3 spin liquid.

Professor Kwang-Yong Choi stated, "The realization of the 1/9 magnetization plateau in a kagome spin lattice under applied magnetic fields marks a breakthrough in the study of novel quantum materials. This research is expected to contribute to future applications in quantum computing, particularly in the development of highly stable qubits and topological quantum computation based on spin liquid states.“

This research was conducted in collaboration with Dr. Dirk Wulferding and Dr. Sungkyun Choi from the Institute for Basic Science (IBS), as well as Professor Ki-Hoon Kim’s team at Seoul National University. The study was supported by the National Research Foundation of Korea (NRF) and was published online in Nature Physics (Impact Factor: 18.1, JCR Top 5%) on January 12, 2024. Furthermore, it was featured in Nature Physics' "News &Views" section on February 12, 2024, under the title "A kagome antiferromagnet reaches its quantum plateau.“

※ Title: One-ninth magnetization plateau stabilized by spin entanglement in a kagome antiferromagnet

※ Link: https://www.nature.com/articles/s41567-023-02318-7

Illustration and observation of Dirac spinons in the kagome lattice and the 1/9 magnetization plateau in the magnetization curve