Thermal-transport measurements in a quantum spin-liquid state of the frustrated triangular magnet κ-(BEDT-TTF)2Cu2(CN)3
Thermal-transport measurements in a quantum spin-liquid state of the frustrated triangular magnet κ-(BEDT-TTF)2Cu2(CN)3
复制标题
DOI：
10.1038/nphys1134
复制
发表时间：
2009-01-01
期刊：
影响因子：
19.6
通讯作者：
Matsuda, Yuji
中科院分区：
文献类型：
--
作者：
Yamashita, Minoru;Nakata, Norihito;Matsuda, Yuji
量子自旋液体（QSLs）的概念，具有量子涨落驱动的无序基态的反铁磁体，现在在一维（1D）自旋系统及其阶梯表兄弟中牢固地建立起来。自旋为1/2的有机绝缘体kappa-（双（乙二硫代）-四硫代富勒烯）(2)Cu-2(CN)(3) (kappa-(BEDT-TTF)(2)Cu-2(CN)(3)；参考文献1)具有二维三角形晶格结构，很可能是D >= 2中这种奇异态的第一个实验实现。至关重要的是揭示低洼基本自旋激发的性质（2,3），特别是“自旋间隙”的存在/不存在，这将为这个假定的QSL的普适类提供重要信息。在这里，我们报告了我们在80mk下进行的热输运测量。我们意外地发现，没有间隙激发的明确证据，这与最近的热容测量报告大相径庭(4)。这个有趣的系统的低能物理需要根据目前的结果重新解释一个自旋间隙的QSL相。
The notion of quantum spin-liquids (QSLs), antiferromagnets with quantum fluctuation-driven disordered ground states, is now firmly established in one-dimensional (1D) spin systems as well as in their ladder cousins. The spin-1/2 organic insulator kappa-(bis(ethylenedithio)-tetrathiafulvalene)(2)Cu-2(CN)(3) (kappa-(BEDT-TTF)(2)Cu-2(CN)(3); ref. 1) with a 2D triangular lattice structure is very likely to be the first experimental realization of this exotic state in D >= 2. Of crucial importance is to unveil the nature of the low-lying elementary spin excitations(2,3), particularly the presence/absence of a 'spin gap', which will provide vital information on the universality class of this putative QSL. Here, we report on our thermal-transport measurements carried out down to 80 mK. We find, rather unexpectedly, unambiguous evidence for the absence of a gapless excitation, which sharply contradicts recent reports of heat capacity measurements(4). The low-energy physics of this intriguing system needs be reinterpreted in light of the present results indicating a spin-gapped QSL phase.