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arXiv 1012.2368cond-mat.supr-con
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高温超导的配对机制:实验限制

Pairing mechanism of high-temperature superconductivity: Experimental constraints

Guo-meng Zhao

摘要:

铜氧化物高温超导理论的发展是物理学中的突出问题之一。这是一个二十多年来击败理论物理学家的挑战。试图理解这个问题是阻碍了一些机制之间的微妙的相互作用,并在这些系统中存在几个几乎退化和竞争的阶段。在这里,我们提出了一些关键的实验,放置在高温超导的配对机制的基本约束。在铜酸盐中观察到的非常规氧同位素效应清楚地表明了强的电子-声子相互作用和极化子和/或双极化子的存在。角分辨光电子能谱和隧穿谱为多声子模的强耦合提供了直接证据。相比之下,这些光谱不显示预期的磁共振模式的强耦合功能。角分辨光电子能谱和氧同位素效应对未掺杂母体化合物的反铁磁交换能J的影响一致表明,极化子结合能约为2 eV,比J = 0.14 eV大一个数量级以上.空穴掺杂铜氧化物的正常态自旋极化率数据表明,在欠掺杂区,位间双极化子是主要的载流子,而在过掺杂区,类费米液体极化子是主要的.所有检验能隙对称性或序参量对称性的实验都一致地表明,类费米液体组分的本征能隙(配对)对称性是各向异性s波,双极化子的玻色-爱因斯坦凝聚的序参量对称性是d波。

英文摘要:

Developing a theory of high-temperature superconductivity in copper oxides is one of the outstanding problems in physics. It is a challenge that has defeated theoretical physicists for more than twenty years. Attempts to understand this problem are hindered by the subtle interplay among a few mechanisms and the presence of several nearly degenerate and competing phases in these systems. Here we present some crucial experiments that place essential constraints on the pairing mechanism of high-temperature superconductivity. The observed unconventional oxygenisotope effects in cuprates have clearly shown strong electron-phonon interactions and the existence of polarons and/or bipolarons. Angle-resolved photoemission and tunneling spectra have provided direct evidence for strong coupling to multiple-phonon modes. In contrast, these spectra do not show strong coupling features expected for magnetic resonance modes. Angle-resolved photoemission spectra and the oxygen-isotope effect on the antiferromagnetic exchange energy J in undoped parent compounds consistently show that the polaron binding energy is about 2 eV, which is over one order of magnitude larger than J = 0.14 eV. The normal-state spin-susceptibility data of holedoped cuprates indicate that intersite bipolarons are the dominant charge carriers in the underdoped region while the component of Fermi-liquid-like polarons is dominant in the overdoped region. All the experiments to test the gap or order-parameter symmetry consistently demonstrate that the intrinsic gap (pairing) symmetry for the Fermi-liquid-like component is anisotropic s-wave and the order-parameter symmetry of the Bose-Einstein condensation of bipolarons is d-wave.

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