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arXiv 0904.4603cond-mat.str-elcond-mat.mtrl-sci
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LaMnO3中Jahn-Teller畸变和轨道序的起源

Origin of Jahn-Teller distortion and orbital-order in LaMnO3

Eva Pavarini, Erik Koch

摘要:

LaMnO 3中的合作Jahn-Teller畸变和轨道序的起源是锰氧化物物理学的核心。同时存在的四角晶系和GdFeO_3型畸变以及e_g和t_2g电子之间强的Hund规则耦合使问题复杂化。为了澄清这种情况,我们使用局域密度近似+动力学平均场方法计算了Kugel-Khomskii超交换机制的转变温度,并将超交换效应与晶格畸变效应分开。我们发现,仅超交换就能得到T_KK=650 K。而四方晶系和GdFeO_3型畸变使T_KK降低到550 K。因此,电子-声子耦合是必不可少的,以解释当地的Jahn-Teller扭曲的持久性,至少1150 K,并再现从中子散射推导出的占据轨道。

英文摘要:

The origin of the cooperative Jahn-Teller distortion and orbital-order in LaMnO3 is central to the physics of the manganites. The question is complicated by the simultaneous presence of tetragonal and GdFeO3-type distortions and the strong Hund's rule coupling between e_g and t_2g electrons. To clarify the situation we calculate the transition temperature for the Kugel-Khomskii superexchange mechanism by using the local density approximation+dynamical mean-field method, and disentangle the effects of super-exchange from those of lattice distortions. We find that super-exchange alone would yield T_KK=650 K. The tetragonal and GdFeO3-type distortions, however, reduce T_KK to 550 K. Thus electron-phonon coupling is essential to explain the persistence of local Jahn-Teller distortions to at least 1150 K and to reproduce the occupied orbital deduced from neutron scattering.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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