Giant magnetocaloric effect in spin supersolid candidate Na2BaCo(PO4)2

• 成果类型: Article
• 署名作者: Xiang, Junsen; Zhang, Chuandi; Gao, Yuan; Schmidt, Wolfgang; Schmalzl, Karin; Wang, Chin-Wei; Li, Bo; Xi, Ning; Liu, Xin-Yang; Jin, Hai; Li, Gang; Shen, Jun; Chen, Ziyu; Qi, Yang; Wan, Yuan; Jin, Wentao; Li, Wei; Sun, Peijie; Su, Gang
• 署名单位: Chinese Academy of Sciences; Institute of Physics, CAS; Beihang University; Chinese Academy of Sciences; Institute of Theoretical Physics, CAS; Institut Laue-Langevin (ILL); Australian Nuclear Science & Technology Organisation; Tsinghua University; Chinese Academy of Sciences; Technical Institute of Physics & Chemistry, CAS; Fudan University; Fudan University; Chinese Academy of Sciences; University of Chinese Academy of Sciences, CAS; Beihang University; Chinese Academy of Sciences; University of Chinese Academy of Sciences, CAS; Chinese Academy of Sciences; University of Chinese Academy of Sciences, CAS
• 刊物名称: Nature
• ISSN/ISSBN: 0028-3757
• DOI: 10.1038/s41586-023-06885-w
• 发表日期: 2024-01-11
• 页码: 270-275
• 关键词: phase; demagnetization; gas

摘要

Supersolid, an exotic quantum state of matter that consists of particles forming an incompressible solid structure while simultaneously showing superfluidity of zero viscosity(1), is one of the long-standing pursuits in fundamental research(2,3). Although the initial report of He-4 supersolid turned out to be an artefact(4), this intriguing quantum matter has inspired enthusiastic investigations into ultracold quantum gases(5,6,7,8). Nevertheless, the realization of supersolidity in condensed matter remains elusive. Here we find evidence for a quantum magnetic analogue of supersolid-the spin supersolid-in the recently synthesized triangular-lattice antiferromagnet Na2BaCo(PO4)(2) (ref. (9)). Notably, a giant magnetocaloric effect related to the spin supersolidity is observed in the demagnetization cooling process, manifesting itself as two prominent valley-like regimes, with the lowest temperature attaining below 100 mK. Not only is there an experimentally determined series of critical fields but the demagnetization cooling profile also shows excellent agreement with the theoretical simulations with an easy-axis Heisenberg model. Neutron diffractions also successfully locate the proposed spin supersolid phases by revealing the coexistence of three-sublattice spin solid order and interlayer incommensurability indicative of the spin superfluidity. Thus, our results reveal a strong entropic effect of the spin supersolid phase in a frustrated quantum magnet and open up a viable and promising avenue for applications in sub-kelvin refrigeration, especially in the context of persistent concerns about helium shortages