公海555000kk线路检测・(中国)有限公司

摘要

By monitoring the quasiparticle relaxation rates following a pulse of light, we have established a new window into the intrinsic rates of recombination that occur as Cooper pairs become re-established. We have demonstrated the ability to directly perturb and monitor the superconducting gap in cuprates, using near-infrared pump pulses to suppress superconductivity in the low-fluence regime and to fully induce a metastable pseudogap state in the moderate- to high-fluence regime. These results serve both as a vivid demonstration of an ultrafast phase transition involving a topological change in the nature of the Fermi surface of a material, and as a novel probe into the factors that influence the superconducting order parameter. These new results prelude planned trARPES studies of charge-density wave dynamics.  Ultrafast time-resolved ARPES studies of high Tc superconductor reveal a softening of the electron-boson interaction in concomitance with a softening/closure of the superconducting gap. The effect is negligible in the normal state and for a metallic compound, suggesting that the electron-boson interaction might be a booster for pairing in cuprates.

参考文献：
1. Wentao Zhang et al., Nat. Comm. 5, 4959 (2014).
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3. C. Smallwood, Wentao Zhang et al., PRB 89, 115126 (2014).
4. C. Smallwood, Wentao Zhang et al., Science 336, 1137 (2012).
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报告人简介

张文涛，2005年本科毕业于中国科学技术大学物理系，2010年于中国科学院物理研究所获博士学位。2010-2013年在美国劳伦兹伯克利国家实验室做博士后研究。2013年底至今为加州福尼亚大学伯克利分校物理系Assistant Researcher。
主要利用基于真空紫外激光光源的超高分辨角分辨光电子谱和超快激光的时间分辨光电子能谱等尖端实验技术，在高温铜氧化物超导体的电子能谱及动态过程研究等方面作出了多项重要的工作。利用超高分辨ARPES，从实验上观察到铜氧化物超导体中存在一种新的耦合模式，并对高能色散的物理起源做了解释，而且第一次从光电子谱抽取出铜氧化物超导体的动量分辨电子配对自能函数；利用超短、超强脉冲，用具有时间分辨功能的角分辨光电子能谱仪探测到铜氧化物相图中三个不同的温度尺度并且发现结点区电子色散上的扭折与超导能隙存在着密切关系。发表文章30多篇，包括Nature, Science, Nature Communications, Physcal Review Letters文章近十篇。