简介: |
We envision that the holistic multidisciplinary enlightened empirical approach may be most fruitful to higher Tc. It depends on imagination, insight, experience and knowledge from different fields plus courage and luck. Two general steps have been adopted: to discover new compounds guided by experience and insight empirically and to realize novel mechanisms inspired by models theoretically. Until now, successes have come almost exclusively from the former. Of the many theoretical mechanisms proposed, few has led to the discovery of a superconductor with a clear enhanced-Tc. Interfacial mechanism has been one such most explored theoretically and experimentally but without clear evidence for an enhanced Tc. Our recent detection of non-bulk superconductivity with an unexpectedly high onset-Tcs up to 49 K in rare-earth-doped CaFe2As2 (Ca122) single crystals [1] and the report by Xue's group of a Tc up to 50's K in unit-cell FeSe epi-films [2], offer an unusual opportunity for the search for a new paradigm for higher Tc. Through systematic compositional, structural and magnetic investigations, we have shown [3] a doping-level independent Tc, the simultaneous appearance of superparamagnetism and superconductivity, the existence of mesoscopic-2D structures in rare-earth doped Ca122 single crystals and thus provided evidence for the possible interface-enhanced Tc in Fe-based superconductors. Such mesoscopic-structures may be attributed to defects as evident from the presence of superparamagnetism [4] detected in these superconducting samples. Similar observations were also made in the FeSe thin epi-films from Xue. We have observed in the 3-4 unit-cell FeSe-films Meissner effect below 1 Oe with extensive weak-links up to ~ 20 K; unconnected small superconducting patches up to ~ 40 K; and an unusual dispersion of the magnetic susceptibility with frequency up to 70 K. [5] The weak-links and relaxation of the diamagnetic moment observed in the films suggest that the superconducting state of the FeSe films below 20 K may be a glassy state. The experimental results will be presented and the implications discussed.
*The work on FeSe films was carried out in collaboration with Q. K. Xue's group at Tsinghua; on rare-earth doped Ca122 with J. H. Hoffman's group at Harvard.
References
1. B. Lv et al. PNAS USA 108, 15705 (2011).
2. Q. Y. Wang et al. Chin. Phys. Lett. 29, 037402 (2012).
3. F. Y. Wei et al. arXiv 1308.
4. B. Lv et al. arXiv 1308.3129.
5. L. Z. Deng et al. in preparation.
个人简介：
朱经武院士，原籍广东台山，出生于湖南芷江，1962年在台湾成功大学获取理学士学位，1968年在圣地牙哥加州大学获取博士学位。之后在新泽西贝尔实验室从事研究工作，两年后任职于克利夫兰州立大学，1975年获擢升为教授，1979年出任休斯敦大学物理学教授。2001-2009年任香港科技大学校长，现任美国休斯敦大学天普科学讲座教授、物理学系教授及德州超导中心创始主任，台湾综合大学系统（台湾成功大学、台湾中山大学、台湾中兴大学、台湾中正大学）荣誉校长。朱经武院士曾担任多所机构的顾问及客席研究员，包括洛斯阿拉莫斯国家实验室、马歇尔太空飞行中心、阿贡国家实验室等。1987年，朱经武院士在高温超导的研究取得重大突破，成功地发现新超导体，将超导温度提高至90K以上，开创了高温超导及应用的新纪元，打开了高温超导研究的大门。
朱经武院士是美国科学院、美国人文及科学学院、中国科学院、台湾中央研究院、发展中世界科学院和俄罗斯工程学院院士。朱经武院士曾荣获美国科学界最高荣誉的国家科学奖、国际新材料奖、工程界最崇高的约翰弗里茨大奖等。
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