Two energy scales and two distinct quasiparticle dynamics in the superconducting state of underdoped cuprates
Two energy scales and two distinct quasiparticle dynamics in the superconducting state of underdoped cuprates
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DOI：
10.1038/nphys362
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发表时间：
2006-08-01
期刊：
影响因子：
19.6
通讯作者：
Forget, A.
中科院分区：
文献类型：
--
作者：
Le Tacon, M.;Sacuto, A.;Forget, A.
空穴掺杂高温超导体的超导温度Tc具有圆顶状形状作为空穴浓度的函数，在“最佳”掺杂时具有最大Tc。在欠掺杂侧，超导状态通常用一个能量尺度来描述，与d波隙的最大值（在波腹处）相关，其随着掺杂的减少而增加。在这里，我们报告的电子拉曼散射实验，显示了第二个能量尺度的差距功能：在节点处的差距的斜率，这随着掺杂的减少而减少。我们的测量还揭示了两种不同的准粒子动力学;电子相干性持续到节点处的低掺杂水平，而波腹准粒子变得不相干。使用求和规则，我们发现，低频拉曼响应和温度依赖性的超流密度，都控制节点激发，表现在定性类似的方式与掺杂的变化。
The superconducting temperature T-c of hole-doped high-temperature superconductors has a dome-like shape as a function of hole concentration, with a maximum T-c at 'optimal' doping. On the underdoped side, the superconducting state is often described in terms of one energy scale, associated with the maximum of the d-wave gap (at the antinodes), which increases as the doping decreases. Here, we report electronic Raman scattering experiments that show a second energy scale in the gap function: the slope of the gap at the nodes, which decreases with decreasing doping. Our measurements also reveal two distinct quasiparticle dynamics; electronic coherence persists down to low doping levels at the nodes, whereas antinodal quasiparticles become incoherent. Using a sum-rule, we find that the low-frequency Raman response and the temperature dependence of the superfluid density, both controlled by nodal excitations, behave in a qualitatively similar manner with doping variation.