Electron-phonon interaction and superconductivity in hexagonal ternary carbides Nb2 AC (A: Al, S, Ge, As and Sn)
Electron-phonon interaction and superconductivity in hexagonal ternary carbides Nb2 AC (A: Al, S, Ge, As and Sn)
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DOI：
10.1088/2516-1075/ac2c94
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发表时间：
2021-12-01
影响因子：
2.6
通讯作者：
Probert, M. I. J.
中科院分区：
文献类型：
--
作者：
Karaca, E.;Byrne, P. J. P.;Probert, M. I. J.
采用电子-声子相互作用的密度泛函微扰理论，研究了六方晶系Nb（2）AC（A：Al，S，Ge，As和Sn）的超导转变温度Tc。对计算的电子结构和态密度进行了严格的评估，发现费米能级附近的电子态主要由Nb 4d态组成，这是电导率的原因。从电子-声子计算的理论T-c数据与Frohlich模型非常一致，并且该模型被用作计算有效的筛选方法来识别有希望的Nb-CM（2）AX相材料。对于Nb（2）AC（A：Zn、Cd、Al、Ga、In、Tl、Si、Pb和P），该模型表明Nb 2AlC应具有这组中最高的T-c，略低于Nb 2GeC，与Nb 2SC和Nb 2SnC相当。Nb 2AlC超导性的实验研究尚未完成，但这一结果已被全电子-声子计算所证实，其超导机制是Nb 4d态电子与低频声子（特别是由Nb和A元素主导的声学声子和低频光学声子）的相互作用。发现Nb（2）AC（A：Al，S，Ge，As和Sn）的平均电子-声子耦合参数λ分别为0.646，0.739，0.685，0.440和0.614，相应的超导临界温度Tc分别为6.7K，7.7K，9.8K，2.1K和6.3K。
The superconducting transition temperatures T-c of hexagonal Nb(2)AC (A: Al, S, Ge, As and Sn) are investigated using density functional perturbation theory to model the electron-phonon interaction. A critical assessment of the calculated electronic structure and density of states revealed that the electronic states near to the Fermi level are mostly composed of the Nb 4d states, which are responsible for the electrical conductivity. The theoretical T-c data from electron-phonon calculations are in excellent agreement with the Frohlich model, and this model was used as a computationally efficient screening method to identify promising Nb-CM(2)AX phase materials. For Nb(2)AC (A: Zn, Cd, Al, Ga, In, Tl, Si, Pb and P), the model indicated that Nb2AlC should have the highest T-c of this set, a little lower than Nb2GeC and comparable to Nb2SC and Nb2SnC. Superconductivity in Nb2AlC has not been studied experimentally, but this result was confirmed by full electron-phonon calculations, which also revealed that the mechanism for superconductivity is the interactions of Nb 4d-state electrons with low-frequency phonons (in particular, acoustic phonon and low-frequency optical phonons dominated by Nb and the A element). The average electron-phonon coupling parameter was found to be lambda similar to 0.646, 0.739, 0.685, 0.440 and 0.614 for Nb(2)AC (A: Al, S, Ge, As and Sn), respectively, with a corresponding superconducting critical temperature T-c similar to 6.7 K, 7.7 K, 9.8 K, 2.1 K and 6.3 K, respectively.