Novel Pauli-paramagnetic quantum phase in a Mott insulator
Novel Pauli-paramagnetic quantum phase in a Mott insulator
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DOI：
10.1038/ncomms2082
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发表时间：
2012-09-01
影响因子：
16.6
通讯作者：
Matsuda, Y.
中科院分区：
文献类型：
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作者：
Watanabe, D.;Yamashita, M.;Matsuda, Y.
在莫特绝缘体中，强烈的电子-电子库仑斥力使电子局域化。在大于1的维数中，它们的自旋在低温下通常是反铁磁有序的。几何挫折会破坏这种长程秩序，导致奇异的量子自旋液态。然而，它们的磁性基态长期以来一直是个谜。本文证明了具有二维三角形晶格的有机Mott绝缘体EtMe3Sb[Pd(dmit)(2)](2)（其中Et为C2H5-， Me为CH3-， dmit为1,3-二硫基-2-硫基- 4,5 -二硫基）中的量子自旋液态具有类似泡利顺磁的低能激发，这是流动费米子的标志。我们的转矩磁强计从低温（30 mK）到高磁场（32 T）显示出与半填充的二维金属相当的明显的剩余顺磁化率，证明了基态的磁性无间隙性质。此外，我们的结果对氘化是稳健的，指出了一个扩展的“量子临界相”的出现，其中低能自旋激发表现为具有费米表面的顺磁性金属，尽管有冻结的电荷自由度。
In Mott insulators, the strong electron-electron Coulomb repulsion localizes electrons. In dimensions greater than one, their spins are usually ordered antiferromagnetically at low temperatures. Geometrical frustrations can destroy this long-range order, leading to exotic quantum spin liquid states. However, their magnetic ground states have been a long-standing mystery. Here we show that a quantum spin liquid state in the organic Mott insulator EtMe3Sb[Pd(dmit)(2)](2) (where Et is C2H5-, Me is CH3-, and dmit is 1,3-dithiole-2-thione-4, 5-dithiolate) with two-dimensional triangular lattice has Pauli-paramagnetic-like low-energy excitations, which are a hallmark of itinerant fermions. Our torque magnetometry down to low temperatures (30 mK) up to high fields (32 T) reveals distinct residual paramagnetic susceptibility comparable to that in a half-filled two-dimensional metal, demonstrating the magnetically gapless nature of the ground state. Moreover, our results are robust against deuteration, pointing toward the emergence of an extended 'quantum critical phase', in which low-energy spin excitations behave as in paramagnetic metals with Fermi surface, despite the frozen charge degree of freedom.