Lan Feng, Ma Zongqing, Liu Yongchang, Chen Ning, Cai Qi, Li Huijun, Barua Shaon, Patel Dipak, Al Hossain M Shahriar, Kim Jung Ho, Dou Shi Xue
Tianjin Key Laboratory of Composite and Functional Materials, School of Materials Science &Engineering, Tianjin University, Tianjin 300072, People's Republic of China.
1] Tianjin Key Laboratory of Composite and Functional Materials, School of Materials Science &Engineering, Tianjin University, Tianjin 300072, People's Republic of China [2] Institute for Superconducting and Electronic Materials, University of Wollongong, New South Wales, 2500, Australia.
Sci Rep. 2014 Sep 26;4:6481. doi: 10.1038/srep06481.
To search a proper dopant to further improve superconductivity in 11 type Fe-based superconductors makes sense to both their superconductivity mechanism and possible technological applications. In present work, Mg doped FeSe polycrystalline bulks were obtained by a two-step solid-state reaction method. Even though there are many MgSe and iron impurities existing in the Mg heavy doped FeSe bulks, they exhibit obviously increased Tc compared to undoped FeSe sample. It was found that Mg addition has little effect on the crystal lattice parameters of superconducting β-FeSe, whereas leads to the formation of nano-layered grain structure consisted of MgSe and β-FeSe with similar X-ray diffraction characteristics. Lots of nano-structural interfaces between FeSe and MgSe formed in this homogenous layered grain structure have significant effect on the superconducting properties and are responsible for the enhancement of Tc, as like the case of FeSe thin film on some specific substrates. Our work not only demonstrates a powerful way for raising Tc in bulk superconductors, but also provides a well-defined platform for systematic studies of the mechanism of unconventional superconductivity by considering interface effect.
寻找一种合适的掺杂剂以进一步提高11型铁基超导体的超导性，这对其超导机制和可能的技术应用都具有重要意义。在本工作中，通过两步固态反应法制备了Mg掺杂的FeSe多晶块体。尽管在Mg重掺杂的FeSe块体中存在许多MgSe和铁杂质，但与未掺杂的FeSe样品相比，它们的Tc明显提高。研究发现，Mg的添加对超导β-FeSe的晶格参数影响很小，却导致形成了由具有相似X射线衍射特征的MgSe和β-FeSe组成的纳米层状晶粒结构。在这种均匀层状晶粒结构中形成的大量FeSe和MgSe之间的纳米结构界面，对超导性能有显著影响，并导致Tc升高，这与在某些特定衬底上的FeSe薄膜情况类似。我们的工作不仅展示了一种提高块状超导体Tc的有效方法，还通过考虑界面效应，为系统研究非常规超导机制提供了一个明确的平台。
