Quantum liquid from strange frustration in the trimer magnet Ba4Ir3O10
Quantum liquid from strange frustration in the trimer magnet Ba4Ir3O10
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DOI：
10.1038/s41535-020-0232-6
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发表时间：
2020-05-06
影响因子：
5.7
通讯作者：
Kimchi, Itamar
中科院分区：
文献类型：
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作者：
Cao Gang;Zheng Hao;Kimchi, Itamar
磁绝缘体等量子自旋系统通常表现出磁序，但这种经典态可以通过两种已知的挫折机制让位于具有奇异纠缠的量子液体：三角形图案晶格中的几何挫折，以及Kitaev蜂窝晶格中精确可解量子液体中的自旋轨道耦合挫折。在这里，我们提出了一种新的受抑量子液体的实验观察出现在一个不太可能的地方：磁性绝缘体Ba 4 Ir 3 O 10，其中Ir 3 O 12三聚体形成一个未受抑的正方形晶格。晶体结构显示没有明显的自旋链。在实验中，我们发现了一个量子液体状态持续到0.2 K，是稳定的强反铁磁相互作用与居里-外斯温度范围从-766到-169 K由于磁各向异性。各向异性平均阻挫参数为2000，在虹彩中很少见到。热容和热导率在低温下都是线性的，这在金属中是一个熟悉的特征，但在这里，绝缘体指向一种奇异的量子液态;仅仅2%的Sr取代Ba在130 K产生长程有序，并破坏了线性T特征。虽然在Ba 4 Ir 3 O 10的Ir 4+（5d（5））离子似乎形成面共享IrO 6八面体的Ir 3 O 12三聚体，我们建议，减少了内部三聚体交换和晶格重组成一个阵列的耦合一维链与额外的自旋。解耦的一维链的极限可以解释大多数但不是所有的惊人的实验观察，表明链间耦合在导致这种量子液体的挫折机制中起着重要作用。
Quantum spin systems such as magnetic insulators usually show magnetic order, but such classical states can give way to quantum liquids with exotic entanglement through two known mechanisms of frustration: geometric frustration in lattices with triangle motifs, and spin-orbit-coupling frustration in the exactly solvable quantum liquid of Kitaev's honeycomb lattice. Here we present the experimental observation of a new kind of frustrated quantum liquid arising in an unlikely place: the magnetic insulator Ba4Ir3O10 where Ir3O12 trimers form an unfrustrated square lattice. The crystal structure shows no apparent spin chains. Experimentally we find a quantum liquid state persisting down to 0.2 K that is stabilized by strong antiferromagnetic interaction with Curie-Weiss temperature ranging from -766 to -169 K due to magnetic anisotropy. The anisotropy-averaged frustration parameter is 2000, seldom seen in iridates. Heat capacity and thermal conductivity are both linear at low temperatures, a familiar feature in metals but here in an insulator pointing to an exotic quantum liquid state; a mere 2% Sr substitution for Ba produces long-range order at 130 K and destroys the linear-T features. Although the Ir4+(5d(5)) ions in Ba4Ir3O10 appear to form Ir3O12 trimers of face-sharing IrO6 octahedra, we propose that intra-trimer exchange is reduced and the lattice recombines into an array of coupled 1D chains with additional spins. An extreme limit of decoupled 1D chains can explain most but not all of the striking experimental observations, indicating that the inter-chain coupling plays an important role in the frustration mechanism leading to this quantum liquid.