Acoustic plasmons and conducting carriers in hole-doped cuprate superconductors
Acoustic plasmons and conducting carriers in hole-doped cuprate superconductors
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DOI：
10.1103/physrevb.105.235105
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发表时间：
2020-06
期刊：
影响因子：
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通讯作者：
A. Singh;H. Huang;C. Lane;J. H. Li;J. Okamoto;S. Komiya;R. Markiewicz;A. Bansil;A. Fujimori;C. Chen;D. J. Huang
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文献类型：
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作者：
A. Singh;H. Huang;C. Lane;J. H. Li;J. Okamoto;S. Komiya;R. Markiewicz;A. Bansil;A. Fujimori;C. Chen;D. J. Huang
铜酸盐的超导性自几十年前被发现以来一直是个谜，它是通过将电子或空穴掺杂到莫特绝缘体中而产生的。然而，铜酸盐中存在固有的电子-空穴不对称性。铜酸盐的层状晶体结构能够实现与三维金属（即声等离激元）根本不同的集体电荷激发。最近通过共振非弹性 X 射线散射 (RIXS) 在电子掺杂的铜酸盐中观察到声等离子体激元；相比之下，尽管进行了大量测量，但没有证据表明空穴掺杂铜酸盐中存在声等离子体。这种对比促使我们研究铜酸盐 La$_{2-x}$Sr$_x$CuO$_4$ 中的掺杂空穴是否是导电载流子，或者是否太不相干而无法诱导集体电荷激发。在这里，我们提出动量分辨 RIXS 测量和通过损失函数计算集体电荷响应，以协调上述问题。我们的结果为声等离激元和空穴掺杂铜酸盐中长期以来寻找的导电 p 空穴提供了前所未有的光谱证据。
The superconductivity of cuprates, which has been a mystery ever since its discovery decades ago, is created through doping electrons or holes into a Mott insulator. There, however, exists an inherent electron-hole asymmetry in cuprates. The layered crystal structures of cuprates enable collective charge excitations fundamentally different from those of three-dimensional metals, i.e., acoustic plasmons. Acoustic plasmons have been recently observed in electron-doped cuprates by resonant inelastic X-ray scattering (RIXS); in contrast, there is no evidence for acoustic plasmons in hole-doped cuprates, despite extensive measurements. This contrast led us to investigate whether the doped holes in cuprates La$_{2-x}$Sr$_x$CuO$_4$ are conducting carriers or are too incoherent to induce collective charge excitation. Here we present momentum-resolved RIXS measurements and calculations of collective charge response via the loss function to reconcile the aforementioned issues. Our results provide unprecedented spectroscopic evidence for the acoustic plasmons and long sought conducting p holes in hole-doped cuprates.