Electron – phonon theory of ferroelectricity and the isotope effect in perovskite oxides
Electron – phonon theory of ferroelectricity and the isotope effect in perovskite oxides
复制标题
铁电性的电子-声子理论和钙钛矿氧化物中的同位素效应
DOI：
10.1080/00150199908230292
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发表时间：
1999
期刊：
影响因子：
0.8
通讯作者：
N. Kristoffel
中科院分区：
文献类型：
--
作者：
P. Konsin;N. Kristoffel
钙钛矿型氧化物(BaTiO_3等)氧的2p态(价带)和钛的3d态(导带)通过主动振动的动态带间杂化导致了铁电性。考虑了Ti(Nb)3d态和O2p态之间的电子-声子相互作用，得到了这类振动铁电体的自由能。电子与应变的耦合，声子和电子-声子的非谐性，包括带间的非线性电子-声子相互作用和声子与声子的耦合。电子-声子相互作用导致了TO声子软频率表达式中本质的高阶顶点项。结果表明，轻同位素富集型铁电材料比高同位素铁电材料具有更高的T_c。计算得到的BaTiO_3的ts(Δ_M)线与实验相符。
Abstract In perovskite oxides (BaTiO3, etc.) the dynamical interband hybridization of the oxygen 2p states (the valence band) and the titanium 3d states (the conduction band) by active TO vibrations induces the ferroelectricity. The free energy of such type vibronic ferroelectrics is obtained taking into account the electron – phonon interaction between Ti(Nb) 3d and O 2p states. the coupling of electrons with strains, the phonon and electron – phonon anharmonicities, including nonlinear interband electron – phonon interactions and the coupling of TO phonons with acoustical vibrations. Electron – phonon interactions lead to essential higherorder vertex terms in the expression for the soft frequency of the TO phonon. It is concluded that a light-isotope-enriched ferroelectric shows higher Tc than a ferroelectric with a heavier isotope as observed. The calculated Ts (ΔM) line for BaTiO3 agrees with the experiment.