Vanishing of phase coherence in underdoped Bi2Sr2CaCu2O8+δ
Vanishing of phase coherence in underdoped Bi2Sr2CaCu2O8+δ
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DOI：
10.1038/18402
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发表时间：
1999-03-18
期刊：
影响因子：
64.8
通讯作者：
Bozovic, I
中科院分区：
文献类型：
--
作者：
Corson, J;Mallozzi, R;Bozovic, I
虽然电子结合成库珀对是形成超导状态的基本条件，但其显著的特性-零电阻和完美的抗磁性-也需要对之间的相位相干性。当相干性在转变温度T-c处丧失时，配对保留，连同在空间和时间上有限的相位相关性。在常规金属中，具有短程相位相干性的库珀对在Tc以上不超过1 K的温度下存活。在低掺杂的高T-c铜氧化物中，在温度T*（大约比T-c高100 K）之前发现了某种形式的配对的光谱证据（参考文献1-3）。这种配对和库珀对的形成是如何联系在一起的，这是高温超导中的一个中心问题。这种关系的性质取决于在正常状态下相位相关伴随配对的程度（4）。在这里，我们报告测量的高频电导率跟踪的相位相关时间τ在正常状态下的Bi 2Sr 2CaCu 2 O 8 + δ，s家庭的欠掺杂的氧化铜超导体。在T-c之上，我们发现τ反映了相或涡旋中热生成的拓扑缺陷的运动（5，6）。然而，涡旋增殖减少τ值无法区分正常状态的电子在100 K的寿命，远低于T*。
Although the binding of electrons into Cooper pairs is essential in forming the superconducting state, its remarkable properties-zero resistance and perfect diamagnetism-require phase coherence among the pairs as well. When coherence is lost at the transition temperature T-c, pairing remains, together with phase correlations which are finite in space and time. In conventional metals, Cooper pairs with short-range phase coherence survive no more than 1 K above T-c. In underdoped high-T-c copper oxides, spectroscopic evidence for some form of pairing is found up to a temperature T*, which is roughly 100 K above T-c (refs 1-3). How this pairing and Cooper-pair formation are related is a central problem in high-T-c superconductivity. The nature of this relationship hinges on the extent to which phase correlations accompany pairing in the normal state(4). Here we report measurements of high-frequency conductivity that track the phase-correlation time tau in the normal state of the Bi2Sr2CaCu2O8+delta,s family of underdoped copper oxide superconductors. Just above T-c,we find that tau reflects the motion of thermally generated topological defects in the phase, or vortices(5,6). However, vortex proliferation reduces tau to a value indistinguishable from the lifetime of normal-state electrons at 100 K, well below T*.