LiFeAs的超导电性
 ( The superconductivity at 18 K in LiFeAs system )

X. C. Wang, Q. Q. Liu, Y. X. Lu, W. B. Gao, L. X. Yang, F. Y. Li, R. C. Yu, C. Q. Jin

arXiv:0806.4688

Solid State Communications 148, 538-540 (2008)

Cited by Prof. Hosono in his Review Article J. Phys. Soc.Jpn. 78, 062001, 2009
Reviewed in a feature article of Physics Today, 62, 36 (2009)
Top cited article from 2005 to 2010
Cite times: >300, as of December 2011

   The recent discovery of superconductivity in iron arsenide compounds RFeAsO ( R= rare earth) or AFe2As2 (A = alkaline earth) has attracted great attention due to the unexpected high Tc in the system containing ferromagnetic elements like Fe. Similar to high Tc cuprates, the superconductivity in iron arsenide is related to a layered structure. Searching for new superconductors with [FeAs] layer, but of simpler structure will be of scientific significance either to build up new multilayered superconductors that may reach higher Tc or to study the mysterious underlined superconducting mechanism in iron arsenide compounds. Here we report that a new superconducting iron arsenide system LiFeAs was found. The compound crystallizes into a structure containing [FeAs] conducting layer that is interlaced with Li charge reservoir. Superconductivity was observed with Tc up to 18 K in the compounds.

     

   自从 2008 年 3 月 日本东京工业大学 Hosono 小组报道了超导转变温度为 26K 的 La(O 1-x F x )FeAs 超导体后,迅速掀起了铁基超导体的研究热潮。 除了铜氧化物高温超导体之外,该系列超导体是唯一一个 T c 超过 50K 的超导体系列,其超导转变温度超过了常规 BCS 理论预言电子与声子相互作用所能产生 30 ~ 40K 超导转变温度的极限。

  目前人们已经发现三类铁砷超导体系列(见下图): (i)RFeAsO 或 AFeAsF ( A 为碱土金属)(简称为 1111 )系列; (ii)AFe2 As2 ( A 为碱土金属,简称为 122 )系列; (iii)AFeAs ( A = Li , Na ,简称为 111 )系列。 在新型铁基超导材料的探索中,本实验小组首先发现 “ 111 ” 型铁基超导体 LiFeAs ,观察到 T c 为 18K 的超导转变,并相继合成出T c 约为 26K 的 NaFeAs 超导体以及T c 约为6K的LiFeP超导体。

  除 111 型外,其余类型铁砷超导体均发现有非超导的母体相,通过母体相的元素掺杂来引入载流子,抑制自旋密度波的不稳定,从而出现超导电性。但是到目前为止,所有关于 LiFeAs超导体的研究中均没有发现自旋密度波存在的证据。由于LiFeAs超导体中相邻铁原子间距离最小,所以该铁砷超导体具有显著区别于其它铁砷超导体的性质。

     

1111型              122型               111型