Instability of a quantum spin liquid in an organic triangular-lattice antiferromagnet
Instability of a quantum spin liquid in an organic triangular-lattice antiferromagnet
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DOI：
10.1038/nphys1715
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发表时间：
2010-09-10
期刊：
影响因子：
19.6
通讯作者：
Kato, R.
中科院分区：
文献类型：
--
作者：
Itou, T.;Oyamada, A.;Kato, R.
量子液体——已知在 He-3、He-4 和金属中的电子中实现——通常表现出经典牛顿动力学下不可预见的不稳定性，例如超流体和超导转变。最近，在受抑反铁磁自旋 1/2 系统中发现了一种新的量子液体，现在称为量子自旋液体(1,2)。在这种状态下，自旋的量子涨落即使在绝对为零的情况下也会阻止经典的反铁磁有序性，类似于众所周知的量子液体中的情况。一个仍然悬而未决的基本问题是，在量子自旋液体以及众所周知的量子液体中是否会出现经典有序以外的不稳定性。在这里，我们通过实验证明，有机三角晶格反铁磁体中的量子自旋液体会经历涉及对称破缺和/或拓扑排序（3）的不稳定性，可能会产生新的物质量子态。我们的结果揭示了一种新的量子液体不稳定性，它可能成为与已知的费米子液体不稳定性（例如巴丁-库珀-施里弗配对和佩尔斯不稳定性）和玻色子液体不稳定性（玻色-爱因斯坦凝聚）类似的概念。
Quantum liquids-known to be realized in He-3, He-4 and electrons in metals-generally exhibit instabilities unforeseen under classical Newtonian dynamics, such as the superfluid and superconducting transitions. Recently, a new quantum liquid, now known as the quantum spin liquid, has been discovered in frustrated antiferromagnetic spin-1/2 systems(1,2). In this state, quantum fluctuations of spins prevent classical antiferromagnetic ordering even at absolute zero, similar to the situation in the well-known quantum liquids. A fundamental question that has remained open is whether instabilities other than classical ordering can occur in a quantum spin liquid, as well as in the well-known quantum liquids. Here we demonstrate experimentally that a quantum spin liquid in an organic triangular-lattice antiferromagnet undergoes an instability involving symmetry breaking and/or topological ordering(3), possibly giving rise to a new quantum state of matter. Our result reveals a new variety of quantum-liquid instability, which might become a comparable concept to the already-known fermion-liquid instabilities (such as Bardeen-Cooper-Schrieffer pairing and Peierls instability) and boson-liquid instability (Bose-Einstein condensation).