轨道序对半掺杂锰氧化物光学性质的影响

在两轨道双交换模型基础上，讨论了电子关联作用对半掺杂锰氧化物轨道序的影响，推导出能计算各个相的光电导公式.结果显示，光吸收与轨道序之间存在关联现象.对于铁磁相，当格点库仑相互作用(U)从无到有逐渐增加时，铁磁相会从无轨道序过渡到有轨道序，相变前 后非相干光吸收有一个从无能隙到有能隙的明显变化.对于层状反铁磁的A相，U的增加会使 轨道序更明显，非相干光吸收部分的能隙随之也增大.关键词：轨道序光电导锰氧化物库仑相互作用

Affect of the orbital ordering in half-doped manganites on their optical propert ies

Based on the two-orbital double-exchange model, we discuss the affect of the on- site Coulomb interaction on the orbital ordering in hafl-doped manganites and de rive a formula of the optical conductivity for various phases of half-doped mang anites. The results show that there exists a correlation between the orbital ord ering and the optical absorption. For the magnetic phase (FM), with the transiti on from orbital-disordered to orbital-ordered states induced by the on-site Coul omb interaction(U),the incoherent optical absorption we calculate is substantial ly different. For the layered antiferromagnetic phase (A), the increase of the o n-site Coulomb interaction enlarges the orbital ordering. As a result, the energ y gap in the incoherent absorption is also widened.