极性三元混晶中的Wannier激子结合能

Binding Energies of Wannier Excitonsin Polar Ternary Mixed Crystals

摘要:

在无序元胞孤立位移(MREI)模型下．考虑激子与混晶中的两支光学声子的相互作用，利用变分法计算了极性三元混晶(TMCs)中的Wannier激子的结合能。数值计算给出几种混晶材料的结合能随组份x的变化关系。讨论了混晶中的两支光学声子对激子结合能的贡献。结果表明，当电子和空穴有效质量相差较大时，电声子相互作用对激子结合能有着重要的贡献，声子对结合能的影响随混晶组份非线性变化的。同时讨论了有效声子近似(EPMA)在计算激子结合能时的适用范围。

Abstract:

Binding energies of Wannier excitons in ternary mixed crystals(TMGs) of polar crystals were variationally calculated by taking the interaction between the exciton and two branches of optical phonon modes into account in the modified random-element-isodisplacement(MREI) model.The numerical results of the excitonic binding energies as functions of the composition x were given for several TMCs.The contributions of the two branches of phonons to the excitonic binding energies were discussed.It is shown that the electron-phonon(e-p) coupling plays an important role for the binding energies of the excitons with larger electron-hole mass differences.A non-linear dependence of the phonon contributions to the binding energies on the composition x is found.The validity of the effective phonon mode approximation(EPMA) to formulate the exciton-phonon interaction was discussed.