温度对于交换作用下的能带劈裂的影响

The Effect of Temperature on Energy Band with Exchange Interaction

晶体中电子之间交叠形成电子的能带.格点的电子之间具有交换作用时使能带劈裂成自旋上下的两个子能带.这样的系统是既具有电子巡游性又具有局域磁矩的系统.当两种自旋的跃迁积分不同时,上下两个能带的形状、宽度、峰高等不同.我们利用格林函数方法研究了温度对于此系统的能带的效应.随着温度升高,两个子能带不断靠近,磁化强度也就不断减小.在一定温度,两个子能带中心完全重合,磁化强度为零.两个子能带的裂距的变化与相交可定性地说明系统随温度的变化出现绝缘体、半导体、金属之间的转变.

In a crystal, when electrons overlap with their neighbors, the system forms the electronic band. The interaction between sites results in that the band splits into spin-up and spin-down sub-bands. The system is magnetic metal model, in which the electrons play roles of both itineracy and localized spins. When hopping exchange a kind of strengths spin-up t ↑ and spin-down t↓are different, the shapes, widths and peaks of the two sub-bands are different. We study with Green＇ s Function Method to research the effect of temperature on the energy band of this system. With the increase of temperature, the band gap between the two sub-band decreases and magnetization intensity drops. At Curie point, the two sub-bands become identical and magnetization intensity becomes zero. It is evident that the change and overlapping of the distancc between the sub-band centers with temperature increasing make out the transition between insulator, semiconductor and metal.