Quantum Paraelectric States in SrTiO3 and KTaO3: Barrett Model, Vendik Model, and Quantum Criticality
Quantum Paraelectric States in SrTiO3 and KTaO3: Barrett Model, Vendik Model, and Quantum Criticality
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DOI：
10.7566/jpsj.85.074703
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发表时间：
2016-07-15
影响因子：
1.7
通讯作者：
Yamaguchi, Toshihisa
中科院分区：
文献类型：
--
作者：
Fujishita, Hideshi;Kitazawa, Shou;Yamaguchi, Toshihisa
测量了量子顺电材料SrTiO_3和KTaO_3在4~325K温度范围内的介电常数，并根据Barrett和Vendik模型分析了它们的温度依赖关系。前者处理铁电光学模式与其他光学模式的耦合，而后者处理与声学模式耦合的模式。此外，后者还包含缺陷密度和不均匀性的度量。低温下的介电常数可以用文迪克公式精确地描述；然而，即使在引入了缺陷密度和不均匀性的测量之后，用巴雷特公式也不能准确地描述它们。最近在经典区域和量子顺电区域之间引入了一个临界量子顺电区域。我们指出，对于铁电模式和声学模式耦合的模型，临界区是很好地实现低温近似的区域。
The dielectric constants of the quantum paraelectrics SrTiO3 and KTaO3 are measured between 4 and 325 K. Their temperature dependences are analyzed on the basis of the Barrett and Vendik models. The former model deals with a ferroelectric optical mode coupled with other optical modes, whereas the latter deals with the mode coupled with acoustic modes. In addition, the latter contains a measure of the density of defects and inhomogeneity. The dielectric constants at low temperatures can be accurately described using Vendik's formula; however, they cannot be accurately described using Barrett's formula, even after the introduction of a measure of the density of defects and inhomogeneity. A critical quantum paraelectric region has been introduced recently between a classical region and a quantum paraelectric one. We point out that the critical region is where a low-temperature approximation is well realized for the model with the coupling between the ferroelectric and acoustic modes.