金属间化合物MgB_2电子结构与超导电性的研究

摘要

利用正电子湮没实验,结合理论模拟计算研究了金属间化合物MgB_2系列样品.结果表明,在不同压强下,样品的电子结构发生了变化,Mg原子层电子向B原子层方向转移,与B原子层面上的空穴载流子复合,导致费米能级降低,其附近的态密度减小,使可配对电子减少;同时由于压力作用,样品材料晶格弹性减弱,电声耦合失匹,抑制了材料的超导电性.最后对激光辐照下的MgB_2系列样品进行了分析,可能在一定光剂量范围内,有助于超导电性,过量的光子掺杂将会抑制其超导电性.%In this paper,the intermetallic compound MgB_2 systems are studied by positron annihilation and theoretical calculation. The results show that,under increasing pressure,the electronic structure changes,and the electrons transfer from Mg layers to B layers. The holes in the B layers are partially filled. Density of states of MgB_2 near Fermi level decreases,hence the reduction of matching electrons. Because of the decreased flexibility of sample lattice and degree of electron-phonon coupling,the superconductivity can be inhibited. Based on the positron annihilation,we speculate that a proper dose of laser irradiation can improve the superconducting characteristics of MgB_2 samples.