Department of Physics, University of Illinois at Chicago, Chicago, IL 60607, USA.
Proc Natl Acad Sci U S A. 2011 Jun 7;108(23):9346-9. doi: 10.1073/pnas.1101008108. Epub 2011 May 23.
In order to understand the origin of high-temperature superconductivity in copper oxides, we must understand the normal state from which it emerges. Here, we examine the evolution of the normal state electronic excitations with temperature and carrier concentration in Bi(2)Sr(2)CaCu(2)O(8+δ) using angle-resolved photoemission. In contrast to conventional superconductors, where there is a single temperature scale T(c) separating the normal from the superconducting state, the high-temperature superconductors exhibit two additional temperature scales. One is the pseudogap scale T(∗), below which electronic excitations exhibit an energy gap. The second is the coherence scale T(coh), below which sharp spectral features appear due to increased lifetime of the excitations. We find that T(∗) and T(coh) are strongly doping dependent and cross each other near optimal doping. Thus the highest superconducting T(c) emerges from an unusual normal state that is characterized by coherent excitations with an energy gap.
为了理解铜氧化物高温超导的起源，我们必须了解它所出现的正常状态。在这里，我们使用角分辨光电子能谱研究了 Bi(2)Sr(2)CaCu(2)O(8+δ)中正常态电子激发随温度和载流子浓度的演化。与传统超导体不同，传统超导体中只有一个单一的温度尺度 T(c) 将正常态与超导态分开，高温超导体表现出另外两个温度尺度。一个是赝能隙尺度 T(∗)，低于这个温度，电子激发表现出能隙。第二个是相干尺度 T(coh)，低于这个尺度，由于激发寿命的增加，会出现尖锐的谱特征。我们发现 T(∗)和 T(coh)强烈依赖于掺杂，并且在最佳掺杂附近相互交叉。因此，最高的超导 T(c)来自于一种异常的正常状态，其特征是具有能隙的相干激发。
