轨道序对半掺杂锰氧化物光学性质的影响

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

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 .

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 derive a formula of the optical conductivity for various phases of half-doped manganites. The results show that there exists a correlation between the orbital ordering and the optical absorption. For the magnetic phase (FM), with the transition from orbital-disordered to orbital-ordered states induced by the on-site Coulomb interaction( U) the incoherent optical absorption we calculate is substantially different. For the layered antiferromagnetic phase (A), the increase of the on-site Coulomb interaction enlarges the orbital ordering. As a result, the energy gap in the incoherent absorption is also widened.