利用第一性原理计算分析Bi-2212超导机理及H_2S零电阻现象的成因  

Analysis of the Bi-2212 Superconducting Mechanism and the Reason of H_2S Zero-Resistance Phenomenon by First Principle Calculations

作　　者：卢天倪 孙昱艳[3,2] 齐铭[4,2] 周廉[1,2] 

机构地区：[1]西安交通大学材料金属材料强度国家重点实验室,陕西西安710049 [2]西北有色金属研究院超导材料研究所,陕西西安710016 [3]西安建筑科技大学,陕西西安710055 [4]西安航空学院,陕西西安710077

出　　处：《中国材料进展》2017年第5期344-351,共8页Materials China

基　　金：陕西省自然科学基金资助(项目号2015JQ5154;2016 JQ5057)

摘　　要：利用第一性原理分别对掺杂的Bi-2212高温超导材料以及高压下的H_2S分子中各元素的分波态密度谱(PDOS)进行了计算。根据计算结果对Bi-2212的超导转变温度Tc随掺杂含量的改变而变化,以及H_2S在高压下的零电阻现象进行了分析。在Bi-2212超导材料处于最佳掺杂含量时,电子能量接近于费米面附近的超导赝能隙,从而降低了形成超导电子对所需的凝聚能,因此这些电子转变为超导电子对。另外,靠近费米面处的电子态密度在最佳掺杂量时达到最大值,即能够被诱导为库伯对的电子数量增多,在上述两方面的共同作用下,电子在较高的温度下能够更容易转变为超导电子对,因此超导转变温度提高。同时对高压下的H_2S晶体的PDOS谱进行了计算,根据计算的结果分析得到,高压下的H_2S由于晶格的收缩破坏了原子之间的成键,使得电子的分布已经不满足泡利不相容原理,而是以一种类似于"团聚"的形式存在。当对高压下的H_2S加载电压后,这些"团聚"的电子能够作为载流子移动从而形成电流,在此过程中,电子之间很难发生碰撞,其总动量的改变量可以认为是零,这是造成高压下的H_2S能够在室温范围内表现出"零电阻"现象的成因。In this paper, the Partial Density of States （PDOS） of each element in doped Bi- 2212 high temperature superconductor and H2 S under high pressure is calculated by the first principle. According to the calculation results, we made analysis on the phenomenon that the critical temperature （Tc） of high temperature superconductor （HTS） Bi -2212 varies with doping content changing. When the Bi -2212 doping content is optimal, the electron energy is near the superconducting constrain gap, also the cohesive energy that the becoming of Cooper Pair electrons needed is decreasing, so these electrons can turn into the superconducting cooper pairs more easily under the optimal content. In addition, with the optimal doping content, the densities of the superconductive electronics near Fermi surface increase to the maximum, which causes the num- ber of becoming Cooper Pair electrons is increasing. Base on the two factors discussed above, the electrons can be induced to the superconducting electrons under higher temperature, thus the transition temperature of Bi - 2212 increases. Last, this paper also discussed the calculation of H2 S under high pressure, it is known from the calculating results that the bond between the atoms can be destroyed because of the lattice contraction under high pressure. We speculate that the distribution of the elec- trons does not satisfy the Pauli Exclusion Principle under high pressure, but in a form liking ＂crowded＂. When H2S is loaded voltage under high pressure, the ＂crowded＂ electrons can move as the carrier and form the electronic current. In the processing collision does not occur between electrons, thus the variation of the electron momentum is zero, so H2S shows the zero resistance phenomenon in the room temperature under high pressure.

关 键 词：H2S Bi-2212掺杂 分波态密度谱 电子团聚 第一性原理计算 

分 类 号：TP391.9[自动化与计算机技术—计算机应用技术]