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学术报告(9.18):铁基超导机理的统一认识

强磁场科学论坛邀请到南京大学闻海虎教授访问中心,并为中心的老师和同学作报告,欢迎大家参加。

时间:9月18日(周二)14:00

地点:强磁场五楼大会议室

报告题目:铁基超导机理的统一认识

报告摘要:

The iron based superconductors are expected to have strong potential in electricity transport, high magnetic field and sensitive magnetic detection. One of the on-going frontier studies on iron based superconductors is about the pairing mechanism. The Fermi surfaces in different systems are extremely distinct: some have both electron and hole pockets, but others have only the electron pockets. Therefore there is no consensus yet about the pairing gap structure and pairing mechanism. We have conducted extensive STM/STS studies on many different iron based superconductors and try to explore a unified understanding of the pairing mechanism.

We found clear evidence of the in-gap quasi-particle states induced by the non-magnetic Cu impurities in Na(Fe0.97-xCo0.03Cux)As, giving the smoking gun evidence of the S± pairing[1]. Furthermore, we show the presence of the bosonic mode on the tunneling spectrum with the energy identical to that of the neutron resonance energy,which is regarded as a consequence of S± pairing [2].

Concerning the iron chalcogenide superconductors without hole Fermi pockets, for example the recently discovered (Li1-xFex)OHFeSe phase with Tc ?40 K, we have conducted systematic investigations. Our STS spectrum clearly indicates the presence of double superconducting gaps with maximum magnitudes of ?D1=14.3 meV and D2=8.6 meV, indicating a strong coupling pairing. Further analysis based on the quasiparticle interference (QPI) allow us to assign the gaps to different Fermi surfaces[3]. Finally use a phase related technique to detect the superconducting order parameter in the system without hole Fermi surfaces. Our result reveals the sign reversal of order parameters on the Fermi surfaces with onlyelectronpockets[4], and thus unifies the pairing mechanism of iron-based superconductors with or without the hole Fermi pockets. Finally we will touch the physics of BEC-BCS crossover in the iron based superconductor[5]. All these support the conclusion that spin fluctuations play the key role in electron pairing.

Reference

1. Huan Yang, Hai-Hu Wen et al., Nature Communications 4, 2947 (2013).

2. Zhengyu Wang, Hai-Hu Wen et al., Nature Physics 9, 42(2013).

3. Zengyi Du, Huan Yang, Hai-Hu Wen et al., Nature Communications 7, 10565(2016).

4. Zengyi Du, Hai-Hu Wen et al., Nature Physics 14, 134 (2018).

5. Mingyang Chen, Huan Yang, Hai-Hu Wen et al., Nature Communications 9, 970(2018).

报告人简介:

国家杰出青年基金获得者,教育部“长江特聘”教授,国家“万人计划”领军人才,美国物理学会会士。长期从事超导和低温物理研究,在高温超导体磁通动力学,高温超导机理问题和非常规超导材料合成和物理性质研究方面获得一批重要成果。1991年中科院等离子体所博士毕业,1991-1993荷兰自由大学博士后,1996-1998德国洪堡基金学者。目前任南京大学教授,博士生导师,南京大学超导物理和材料研究中心主任,Physica C,npj Quantum Materials Phylosophical Magzine杂志 《物理》杂志,中国科学GChinese Physics Letters的编委。2000年获得中国青年科技奖,2004年获得国家自然科学二等奖(第一获奖人),2009年获得香港求是杰出成就集体奖,2010年获得华人物理学会亚洲成就奖,2013年获得国家自然科学一等奖(第四完成人),科技部目标导向性超导973项目“高温超导材料和物理研究”首席科学家,加拿大国家高等研究计划远东区代表。在包括Nature PhysicsScience Advance, Nature Communications在内的SCI 杂志上发表论文 400 余篇,他人引用超过9000次,h-index 50, 在国内外会议上作邀请报告过百场。


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