Coupling strength of charge carriers to spin fluctuations in high-temperature superconductors
Coupling strength of charge carriers to spin fluctuations in high-temperature superconductors
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DOI：
10.1038/43843
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发表时间：
1999-09-23
期刊：
影响因子：
64.8
通讯作者：
Basov, DN
中科院分区：
文献类型：
--
作者：
Carbotte, JP;Schachinger, E;Basov, DN
在传统超导体中，负责超导性的机制的最直接证据来自隧道实验，其提供了潜在的电子-声子相互作用的清晰图像（1，2）。由于传统超导体中的相干长度很大，隧道过程将几个原子层探测到材料的主体中;通过Eliashberg方程的反演，在声子能量处的电流-电压特性中观察到的结构给出（1）电子-声子谱密度α（2）F（ω）。对于高温氧化铜超导体，情况有所不同，其中相干长度（特别是c轴隧穿）可以非常短。正因为如此，光谱学和中子散射等方法为研究潜在的机制提供了更好的途径，因为它们探测了整体性质。现在可以对各种铜氧化物（3-5）进行红外波长下的精确反射测量和精确的极化中子散射数据，这里我们发现导电载流子（通过红外光谱探测）与自旋涨落谱（通过中子散射测量）中的共振结构强烈耦合。从这些结果推断的耦合强度足以解释铜氧化物的高转变温度，突出了自旋涨落在驱动这些材料的超导性中的突出作用。
In conventional superconductors, the most direct evidence of the mechanism responsible for superconductivity comes from tunnelling experiments, which provide a clear picture of the underlying electron-phonon interactions(1,2), As the coherence length in conventional superconductors is large, the tunnelling process probes several atomic layers into the bulk of the material; the observed structure in the current-voltage characteristics at the phonon energies gives(1), through inversion of the Eliashberg equations, the electron-phonon spectral density alpha(2)F(omega). The situation is different for the high-temperature copper oxide superconductors, where the coherence length (particularly for c-axis tunnelling) can be very short. Because of this, methods such as optical spectroscopy and neutron scattering provide a better route for investigating the underlying, mechanism, as they probe bulk properties. Accurate reflection measurements at infrared wavelengths and precise polarized neutron-scattering data are now available for a variety of the copper oxides(3-5), and here we shaw that the conducting carriers (probed by infrared spectroscopy) are strongly coupled to a resonance structure in the spectrum of spin fluctuations (measured by neutron scattering). The coupling strength inferred from those results is sufficient to account for the high transition temperatures of the copper oxides, highlighting a prominent role for spin fluctuations in driving superconductivity in these materials.