Departments of Applied Physics and Physics, Stanford University, Stanford, CA 94305, USA.
Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory and Stanford University, Menlo Park, CA 94025, USA.
Science. 2019 Nov 29;366(6469):1099-1102. doi: 10.1126/science.aaw8850.
In normal metals, macroscopic properties are understood using the concept of quasiparticles. In the cuprate high-temperature superconductors, the metallic state above the highest transition temperature is anomalous and is known as the "strange metal." We studied this state using angle-resolved photoemission spectroscopy. With increasing doping across a temperature-independent critical value ~ 0.19, we observed that near the Brillouin zone boundary, the strange metal, characterized by an incoherent spectral function, abruptly reconstructs into a more conventional metal with quasiparticles. Above the temperature of superconducting fluctuations, we found that the pseudogap also discontinuously collapses at the very same value of These observations suggest that the incoherent strange metal is a distinct state and a prerequisite for the pseudogap; such findings are incompatible with existing pseudogap quantum critical point scenarios.
在正常金属中，宏观性质是通过准粒子的概念来理解的。在铜酸盐高温超导体中，高于最高转变温度的金属态是反常的，被称为“奇异金属”。我们使用角分辨光发射谱研究了这个状态。随着掺杂量跨越一个温度无关的临界值0.19，我们观察到，在布里渊区边界附近，奇异金属的特征是无规近自由能谱，突然重构为具有准粒子的更常规金属。在超导涨落的温度之上，我们发现赝能隙也在相同的值处突然消失。这些观察结果表明，无规近自由的奇异金属是一个独特的状态，也是赝能隙的前提；这种发现与现有的赝能隙量子临界点情景不兼容。
