摘要
By performing P doping on the Si sites in the topological semimetal Mo_(5)Si_(3),we discover strong-coupling superconductivity in Mo_(5)Si_(3-x)P_(x)(0.5≤x≤2.0).Mo_(5)Si_(3)crystallizes in the W_(5)Si_(3)-type structure with space group of I4/mcm(No.140),and is not a superconductor itself.Upon P doping,the lattice parameter a decreases while c increases monotonously.Bulk superconductivity is revealed in Mo_(5)Si_(3-x)P_(x)(0.5≤x≤2.0)from resistivity,magnetization,and heat capacity measurements.T_(c)in Mo_(5)Si_(1.5)P_(1.5)reaches as high as 10.8 K,setting a new record among the W_(5)Si_(3)-type superconductors.The upper and lower critical fields for Mo_(5)Si_(1.5)P_(1.5)are 14.56 T and 105 mT,respectively.Moreover,Mo_(5)Si_(1.5)P_(1.5)is found to be a fully gapped superconductor with strong electron-phonon coupling.First-principles calculations suggest that the enhancement of electron-phonon coupling is possibly due to the shift of the Fermi level,which is induced by electron doping.The calculations also reveal the nontrivial band topology in Mo_(5)Si_(3).The T_(c)and upper critical field in Mo_(5)Si_(3-x)P_(x) are fairly high among pseudobinary compounds.Both of them are higher than those in NbTi,making future applications promising.Our results suggest that the W_(5)Si_(3)-type compounds are ideal platforms to search for new superconductors.By examinations of their band topologies,more candidates for topological superconductors can be expected in this structural family.
通过对拓扑半金属Mo_(5)Si_(3)的硅位进行磷掺杂,我们发现了Mo_(5)Si_(3-x)P_(x)(0.5≤x≤2.0)中强耦合的超导电性.W_(5)Si_(3)结构的Mo_(5)Si_(3)本身并不具有超导性,随着磷掺杂的增加,其晶格常数a单调减小,而c单调增加.在Mo_(5)Si_(3-x)P_(x)(0.5≤x≤2.0)中,电阻、磁化率和比热测量揭示了其中的体超导特性.Mo_(5)Si_(1.5)P_(1.5)的超导转变温度(T_(c))高达10.8K,创造了W_(5)Si_(3)结构超导体的T_(c)纪录,其上下临界场分别为14.56 T和105 mT,且是一个具有强电子-声子耦合的全能隙超导体.第一性原理计算表明,强的电子-声子耦合可能来自于掺磷所引起的费米面的移动,同时也揭示了Mo_(5)Si_(3)非平庸的能带拓扑性质.Mo_(5)Si_(3-x)P_(x)超导体的T_(c)和上临界场在准二元化合物中相当高,超过了NbTi超导体,具有潜在的应用价值.本文的结果表明W_(5)Si_(3)型结构中可能存在更多的新型超导体,对该体系的研究将有助于拓扑超导体的发现.
作者
Bin-Bin Ruan
Jun-Nan Sun
Yin Chen
Qing-Song Yang
Kang Zhao
Meng-Hu Zhou
Ya-Dong Gu
Ming-Wei Ma
Gen-Fu Chen
Lei Shan
Zhi-An Ren
阮彬彬;孙俊男;陈银;杨清松;赵康;周孟虎;谷亚东;马明伟;陈根富;单磊;任治安(Institute of Physics and Beijing National Laboratory for Condensed Matter Physics,Chinese Academy of Sciences,Beijing 100190,China;Information Materials and Intelligent Sensing Laboratory of Anhui Province,Institutes of Physical Science and Information Technology,Anhui University,Hefei 230601,China;Key Laboratory of Structure and Functional Regulation of Hybrid Materials(Anhui University),Ministry of Education,Hefei 230601,China;School of Materials Science and Engineering,University of Science and Technology Beijing,Beijing 100083,China;School of Physical Sciences,University of Chinese Academy of Sciences,Beijing 100049,China;Pilot National Laboratory for Marine Science and Technology,Qingdao 266237,China;Songshan Lake Materials Laboratory,Dongguan 523808,China)
基金
supported by the National Key Research and Development Program of China(2018YFA0704200,2021YFA1401800,2018YFA0305602,and 2017YFA0302904)
the National Natural Science Foundation of China(12074414,12074002,and 11774402)
the Strategic Priority Research Program of Chinese Academy of Sciences(XDB25000000)。
