Institut Matériaux Microélectronique Nanosciences de Provence, Faculté St Jérôme, Case 142, F-13397 Marseille Cedex 20, France.
J Phys Condens Matter. 2011 Jan 19;23(2):025503. doi: 10.1088/0953-8984/23/2/025503. Epub 2010 Dec 16.
We present an ab initio and analytical study of the Jahn-Teller effect in two diluted magnetic semiconductors with d(4) impurities, namely Mn-doped GaN and Cr-doped ZnS. We show that the correct insulating electronic structure may be obtained by a proper treatment of the strong electron correlation in the 3d shell in combination with the Jahn-Teller distortion which breaks the local symmetry. Using the LSDA + U approach, we treat the zinc-blende and the wurtzite crystal structures of GaN:Mn, as well as zinc-blende ZnS:Cr. We show that the trigonal distortion due to the wurtzite structure is less important than the Jahn-Teller deformation. This observation allows us to construct a simplified phenomenological ligand field theory (trigonal influence is neglected) which completes the ab initio part. Our work corrects previous studies and the obtained energy gain due to the Jahn-Teller effect (from both the LSDA + U calculation and the ligand field theory) is in good agreement with the experimental data. The same is true for the complete set of crystal field parameters obtained from the phenomenological model which agrees well with previous optical measurements.
我们对具有 d(4) 杂质的两种稀释磁性半导体（即 Mn 掺杂 GaN 和 Cr 掺杂 ZnS）中的 Jahn-Teller 效应进行了从头算和分析研究。我们表明，通过适当处理 3d 壳层中的强电子相关以及打破局部对称性的 Jahn-Teller 变形，可以获得正确的绝缘电子结构。我们使用 LSDA + U 方法处理闪锌矿和纤锌矿结构的 GaN:Mn 以及闪锌矿结构的 ZnS:Cr。我们表明，由于纤锌矿结构导致的三方畸变比 Jahn-Teller 变形要小。这一观察结果使我们能够构建一个简化的唯象配体场理论（忽略三方影响），从而完成从头算部分。我们的工作纠正了以前的研究，并且 Jahn-Teller 效应引起的能量增益（来自 LSDA + U 计算和配体场理论）与实验数据非常吻合。从唯象模型获得的整套晶体场参数也与以前的光学测量结果非常吻合。
