Thermal-Transport Studies on Two-Dimensional Quantum Spin Liquids
Thermal-Transport Studies on Two-Dimensional Quantum Spin Liquids
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二维量子自旋液体的热传输研究
DOI：
10.1002/cphc.201100556
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发表时间：
2012
期刊：
影响因子：
--
通讯作者：
Y.Matsuda
中科院分区：
文献类型：
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作者：
M.Yamashita;T.Shibauchi;Y.Matsuda
量子自旋液体（QSL）是量子自旋的流体状态，其中长程有序态被量子涨落破坏。 QSL 的基态及其奇异现象已被广泛讨论了数十年，但尚未确定。我们对新发现的 QSL 候选物 κ-(BEDT-TTF)2Cu2(CN)3 和 EtMe3Sb[Pd(dmit)2]2 进行热传输测量，并报告这两种有机绝缘体具有不同的 QSL，其特征在于不同的基本激发。在 κ-(BEDT-TTF)2Cu2(CN)3 中，热传输在低温下被热激活，这表明该 QSL 中存在自旋间隙。与此形成鲜明对比的是，在 EtMe3Sb[Pd(dmit)2]2 中，热导率的相当大的线性温度依赖性在零温度极限下得到了清晰的解决，并且显示出具有长平均自由程（约 1000 个晶格距离）的无间隙激发。如此长的平均自由程证明了 QSL 作为具有长距离相干性的量子凝聚态的一个新特征。
Quantum spin liquids (QSLs) are fluidlike states of quantum spins in which the long‐range ordered state is destroyed by quantum fluctuations. The ground state of QSLs and their exotic phenomena, which have been extensively discussed for decades, have yet to be identified. We employ thermal‐transport measurements on newly discovered QSL candidates κ‐(BEDT‐TTF)2Cu2(CN)3and EtMe3Sb[Pd(dmit)2]2, and report that the two organic insulators have different QSLs characterized by different elementary excitations. In κ‐(BEDT‐TTF)2Cu2(CN)3, heat transport is thermally activated at low temperatures, and this suggests the presence of a spin gap in this QSL. In stark contrast, in EtMe3Sb[Pd(dmit)2]2, a sizable linear temperature dependence of thermal conductivity is clearly resolved in the zero‐temperature limit, and shows gapless excitation with a long mean free path (ca. 1000 lattice distances). Such a long mean free path demonstrates a novel feature of QSL as a quantum‐condensed state with long‐distance coherence.