Modeling polar order in compressively strained SrTiO3
Modeling polar order in compressively strained SrTiO3
复制标题
DOI：
10.1103/physrevb.106.214107
复制
发表时间：
2022-12
影响因子：
3.7
通讯作者：
A. Hallett;J. Harter
中科院分区：
文献类型：
--
作者：
A. Hallett;J. Harter
钛酸锶是一种早期的铁电体，在极低的掺杂水平下出现超导性。值得注意的是，通过应变或化学取代稳定极性相已被证明可以显着提高超导临界温度，并且极性不稳定性在大多数提出的超导配对机制中起着关键作用。因此，对铁电性的严格理解对于阐明这种材料中的电子配对机制至关重要。为了研究钛酸锶中极性序的性质，我们开发了一个简化的自由能模型，该模型仅包括捕获双轴压缩应变系统中相关物理所需的自由度。我们的模型能够计算大型无序系统的能量，精度接近DFT水平。我们用蒙特卡罗方法模拟了铁电和反铁畸变相变，讨论了各种序参量之间的耦合。最后，我们评估极性转变的性质，我们发现既不是严格的位移，也不是有序无序。
Strontium titanate is an incipient ferroelectric in which superconductivity emerges at exceptionally low doping levels. Remarkably, stabilizing the polar phase through strain or chemical substitution has been shown to significantly enhance the superconducting critical temperature, and the polar instability plays a pivotal role in the majority of proposed superconducting pairing mechanisms. A rigorous understanding of ferroelectricity is therefore essential to elucidate the electron pairing mechanism in this material. To investigate the nature of the polar order in strontium titanate, we develop a simplified free energy model that only includes the degrees of freedom necessary to capture the relevant physics in a biaxially compressively strained system. Our model is able to calculate the energies of large, disordered systems with near DFT-level accuracy. We simulate the ferroelectric and antiferrodistortive phase transitions using the Monte Carlo method and discuss the coupling between various order parameters. Finally, we assess the character of the polar transition, which we find to be neither strictly displacive nor order-disorder.