近日，美国橡树岭国家实验室的A. O. Scheie及研究小组与美国田纳西大学的C. D. Batista等人合作并取得一项新进展。经过不懈努力，他们实现三角形反铁磁体KYbSe2中的近似自旋液体和分馏。相关研究成果已于2023年11月6日在国际知名学术期刊《自然—物理学》上发表。
该研究团队近日证实了一种自旋1/2铜铁矿材料KYbSe2，该材料与三角晶格海森堡量子自旋液体具有极高的相似性。借助中子散射技术，他们成功在测量光谱内观测到具有显著下界的扩散连续体。此外，通过应用纠缠目击技术对数据进行分析，研究人员发现多体纠缠能在相邻粒子间传播，并且磁交换耦合的分析也显示出与理论量子自旋液体非常接近的特性。
值得一提的是，关键数据特征已通过施温格玻色子理论和张量网络计算得以再现，证实了实质性的次近邻耦合存在。在布里渊区K点处的动力学结构因子强度在0.3 K时呈现缩放坍缩，暗示着存在二阶量子相变。与此同时，与先前理论工作的对比表明，在较大的次近邻耦合中，近似相呈现为有能隙的Z2自旋液体，这一发现为解决长期以来的争议提供了有力证据。对非弹性中子散射数据的深入分析，包括量子信息理论中纠缠目击的评估，为三角晶格反铁磁体KYbSe2接近自旋液相的观点提供了有力支持。
据悉，尽管海森堡三角晶格量子自旋液体及其向附近磁阶的相变在理论上备受关注，但这些状态的实验表现仍然模糊不清，缺乏清晰的实证证据。
附：英文原文
Title: Proximate spin liquid and fractionalization in the triangular antiferromagnet KYbSe2
Author: Scheie, A. O., Ghioldi, E. A., Xing, J., Paddison, J. A. M., Sherman, N. E., Dupont, M., Sanjeewa, L. D., Lee, Sangyun, Woods, A. J., Abernathy, D., Pajerowski, D. M., Williams, T. J., Zhang, Shang-Shun, Manuel, L. O., Trumper, A. E., Pemmaraju, C. D., Sefat, A. S., Parker, D. S., Devereaux, T. P., Movshovich, R., Moore, J. E., Batista, C. D., Tennant, D. A.
Issue&Volume: 2023-11-06
Abstract: The Heisenberg triangular-lattice quantum spin liquid and its phase transitions to nearby magnetic orders have received much theoretical attention, but clear experimental manifestations of these states are rare. Here we demonstrate that a spin-half delafossite material, namely, KYbSe2, shows close proximity to the triangular-lattice Heisenberg quantum spin liquid. Using neutron scattering, we identify a diffuse continuum with a sharp lower bound within the measured spectra. Applying entanglement witnesses to the data indicates multipartite entanglement spread between its neighbours, and an analysis of its magnetic-exchange couplings reveals close proximity to the theoretical quantum spin-liquid phase. The key features of the data are reproduced by Schwinger boson theory and tensor network calculations with a substantial next-nearest-neighbour coupling. The strength of the dynamical structure factor at the Brillouin-zone K point shows a scaling collapse down to 0.3 K, indicating the existence of a second-order quantum phase transition. Comparing this with previous theoretical work suggests that the proximate phase at a larger next-nearest-neighbour coupling is a gapped Z2 spin liquid, resolving a long-debated issue. A detailed analysis of inelastic neutron scattering data, including the evaluation of entanglement witnesses used in quantum information theory, supports the proposal that the triangular-lattice antiferromagnet KYbSe2 is close to a spin-liquid phase.
DOI: 10.1038/s41567-023-02259-1
Source: https://www.nature.com/articles/s41567-023-02259-1