A 'checkerboard' electronic crystal state in lightly hole-doped Ca2-xNaxCuO2Cl2
A 'checkerboard' electronic crystal state in lightly hole-doped Ca2-xNaxCuO2Cl2
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DOI：
10.1038/nature02861
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发表时间：
2004-08-26
期刊：
影响因子：
64.8
通讯作者：
Davis, JC
中科院分区：
文献类型：
--
作者：
Hanaguri, T;Lupien, C;Davis, JC
空穴掺杂铜氧化物的相图显示在零温度下存在四种不同的电子相。其中常见的有莫特绝缘体、高转变温度超导体和金属相。第四个阶段，未知的身份，发生在轻掺杂沿着零温度边界的“赝隙”制度（1）。这个区域有很多奇特的电子现象，促使许多人提出它包含某种形式的隐藏的电子秩序。在这里，我们提出了低温电子结构成像研究的轻空穴掺杂的氧化铜：Ca 2-xNaxCuO 2Cl 2。隧道光谱（在能量\E\ > 100毫电子伏）显示电子提取概率大大超过那些注入，预期掺杂莫特绝缘体。然而，对于| E |< 100 meV，光谱表现出以E = 0为中心的V形能隙。在此间隙内的状态进行强烈的空间调制，与四个CuO 2单元格的正方形“棋盘”的空间相关性，独立于能量。复杂的原子尺度电子结构变化也存在于棋盘中。这些数据是一致的一个意想不到的晶体电子状态，可能是隐藏的电子顺序，存在于零温度pseudogap制度的Ca 2-xNaxCuO 2Cl 2。
The phase diagram of hole-doped copper oxides shows four different electronic phases existing at zero temperature. Familiar among these are the Mott insulator, high-transition-temperature superconductor and metallic phases. A fourth phase, of unknown identity, occurs at light doping along the zero-temperature bound of the 'pseudogap' regime(1). This regime is rich in peculiar electronic phenomena(1), prompting numerous proposals that it contains some form of hidden electronic order. Here we present low-temperature electronic structure imaging studies of a lightly hole-doped copper oxide: Ca2-xNaxCuO2Cl2. Tunnelling spectroscopy (at energies \E\ > 100 meV) reveals electron extraction probabilities greatly exceeding those for injection, as anticipated for a doped Mott insulator. However, for \E\ < 100 meV, the spectrum exhibits a V-shaped energy gap centred on E = 0. States within this gap undergo intense spatial modulations, with the spatial correlations of a four CuO2-unit-cell square 'checkerboard', independent of energy. Intricate atomic-scale electronic structure variations also exist within the checkerboard. These data are consistent with an unanticipated crystalline electronic state, possibly the hidden electronic order, existing in the zero-temperature pseudogap regime of Ca2-xNaxCuO2Cl2.