高温超导的理论研究

The physics of high temperature superconducting copper oxide and more recently discovered superconducting pnictide is one of the most challenging problems in modern condensed matter. In this project, we propose to extend our previous theoretical work to study under-doped psuedogap phase in high Tc cuprate by using a phenomenological Green's function theory and to study the pairing symmetry in iron based superconductivity...The phenomenological theory proposed by the PI and his co-worker in 2006 can explain a number of different types of experiments in cuprate. The theory will be applied to study experimentally observed giant proximity effect in cuprate superconductivity, where a very large Josephson tunneling barrier of width 100 to 1000 nm has been observed. The phenomenological theory will also be studied to be derived from microscopic t-J model and by applying renormalized mean field theory the PI and his co-workers developed early. ..The pairing symmetry and possible interplay of different paring couplings in iron based superconductors will be examined in connection with the effect of Zn like non-magnetic impurities. We will use a simple multi-band model including the pairing couplings to study the impurity effect. Numerical calculations will be conducted and our theoretical work will be closely related to the Zn-impurity experiments in 1111 compounds. ..This completion of this project will help us understand further the physics of high Tc cuprate in the underdoped region, and reveal seemingly more complex pairing symmetry in iron based superconductivity.

铜氧化物高温超导和最近发现的铁基高温超导是当代凝聚态物理中最具挑战性的问题之一。我们拟延续和推广我们以前的理论工作，用唯象的格林函数理论来研究铜氧化物超导体欠掺杂区的赝能隙相，研究铁基超导体的配对对称性。..项目负责人与合作者在2006年提出的唯象理论能够解释铜氧化物高温超导中许多不同的实验。在本项目中我们将应用此唯象理论，讨论和解释实验上观察到的铜氧化物超导的巨近邻效应。研究如何从微观的二维t-J模型出发，应用重整化平均场理论推导出此唯象理论。..我们将通过类Zn的非磁性杂质效应来研究铁基超导的配对对称性以及不同配对序参量之间的互动。我们将采用简化的多能带紧束缚模型加上不同对称性的超导耦合来描述体系，用数值模拟及计算来研究非磁性杂质及其对超导的作用，理论结果将和1111体系中的实验结果做比较。

研究了铜氧化物高温超导在欠掺杂区域的理论，解释了实验上观察到的巨声子谱反常及在Bi2Sr2-xLaxCuO6+s中的输运及光电子谱。研究了铁基高温超导中在绝缘价带产生库柏电子对的理论以及多带涡旋的理论。对铜氧化物温超导及铁基高温超导理论有了进一步发展，并解释了一些很有挑战性的实验。对最近发展和发现的在拓扑超导涡旋中心的Majorana零能模作了很好的理论计算，协助实验人员发现了此一重要新粒子。在项目执行期间，总共发表23篇与项目有关论文。