一维半金属的能态性质研究大学物理系.doc

一维半金属的能态性质研究 摘要 本课题就一维情况下半金属的能态性质进行研究。半金属是性质介于金属和非之间的ABSTRACT The properties of the energy states is studied for the case of the one-dimensional semi-metallic. The semi-metallic is the material between the metal and nonmetal. Firstly, the effect of the perturbation causes energy levels of the moving electrons in the cycle potetial to form the energy band. As the overlap of the semi-metallic band is relatively small, its nature has both metal and semiconductor natures. And then the energy-band theory is used to obtain the energy density for the semi-metallic at a certain temperature. The Fermi energy level of the semi-metal is calculated by use of the density of states. According to the Fermi energy level, the heat capacity and conductivity of the electron are computed for the semi-metallic. At a certain temperature, the affect of the density of energy states is analyzed for the properties of the electronic heat capacity and conductivity in the semi-metallic. KEY WORDS Semi-metallic; Density of the energy state; Fermi energy level; Electronic heat capacity; Conductivity 目 录 前言 ………………………………………………………………………………4 2．半金属的定义………………………………………………………………………6 3. 能带理论和金属电子论……………………………………………………………9 3.1能态密度函数 …………………………………………………………………9 3.2的确定………………………………………………………………………10 3.3电子热容量 ……………………………………………………………………12 3.4 电导率公式……………………………………………………………………13 4. 一维半金属的能态性质研究………………………………………………………19 总结 …………………………………………………………………………………27 致谢 ……………………………………………………………………………………28 参考文献 ………………………………………………………………………………30 前言 传统的半金属是一种由于导带与价带有少量交叠（负带隙宽度）或导带底与价带顶具有相同能量（零带隙宽度），而使其宏观输运性质介于典型的金属与半导体之间的半金属。[1]在半金属磁体的能带结构中，两个自旋子能带分别具有金属性与绝缘性。半金属材料从微观上具有导体和绝缘体双重性质：对一种自旋取向的电子其能带结构呈现金属性，而另一自旋取向的电子其能带结构呈现绝缘体性。[2] 对半金属的研究重未停止过，并且取得许多优秀的研究成果。2009年，瞿婧，周岚运用量子力学的隧穿方法讨论一个铁磁／半金属／铁磁隧道结(FM／HM／FM)中的自旋极化输运和隧道磁电阻(TMR)。[3] 结果表明：当选定半金属材料自旋向上子能带呈现金属性时，自旋向上和自旋向下电子的隧穿系数都表现出共振隧穿特性．发现与a,u和△一△的取值无关，但随着这些量的增加，和一振荡逐渐加快，峰也变得更为尖锐，并且相邻峰之间的间距也逐渐变窄．更重要的是，当这些系数取值合适时，TMR值明显增大．可见，半金属材料对提高隧道结的磁电阻是十分有利的，只要选取合适的参数便能得到较理想的结果，从而有利于提高磁性存