范德华铁电体薄膜中声子与铁子的挠曲应变工程
Flexo-Strain Engineering of Phonons and Ferrons in Thin Films of Van der Waals Ferrielectrics
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中文总结 AI 辅助
该研究采用朗道-金兹堡-德文希尔方法，探究范德华铁电体薄膜中声子与铁子的色散规律，揭示挠曲应变可调控其色散，为相关材料的挠曲应变工程提供了理论基础。
中文摘要 AI 辅助
挠曲电耦合对电极化涨落和弹性应变的影响，会导致块体范德华铁电体中软光声子、声学声子及铁子的色散规律发生显著变化。由于尺寸、梯度和应变效应决定了薄膜的相图与极化行为，因此挠曲耦合和失配应变应会对范德华铁电体薄膜中的声子与铁子色散产生强烈影响，这一假设具有合理性。本研究采用朗道-金兹堡-德文希尔（Landau-Ginzburg-Devonshire）方法，揭示了软声子与铁子的色散强烈依赖于弹性应变的符号和大小，这类弹性应变源于范德华铁电体CuInP2S6的应变薄膜中晶格常数的失配。具体而言，声学声子和铁子的频率在非零波矢k>k_cr时趋于零，其中波矢临界值k_cr由失配应变、挠曲电耦合强度和温度共同决定。随着拉伸应变的增加，声学声子频率归零的现象表明，可能存在由挠曲应变效应诱导的空间调制非公度极性相。本研究得到的分析结果，为范德华铁电体薄膜中软声子与铁子色散的挠曲应变工程开辟了道路。
英文摘要
The influence of the flexoelectric coupling on the fluctuations of electric polarization and elastic strains can lead to the principal changes of the dispersion law of soft optical and acoustic phonons and ferrons in a bulk van der Waals ferrielectric. Since the size, gradient and strain effects determine phase diagrams and polarization behavior in thin films, it is reasonable to assume that the flexocoupling and mismatch strains should have a strong influence on the dispersion of phonons and ferrons in thin ferroelectric films. Using the Landau-Ginzburg-Devonshire approach, in this work we reveal that the dispersion of soft optical and acoustic phonons and ferrons is strongly dependent on the sign and magnitude of elastic strains, which originate from the lattice constants mismatch in thin strained films of van der Waals ferrielectric CuInP2S6. In particular, the frequency of acoustic phonons and ferrons approaches zero at nonzero wavevectors k>k_cr, where the critical value of the wavevector k_cr is determined by the mismatch strain, flexoelectric coupling strength and temperature. Zeroing of the acoustic phonon frequency, that appears with increase of tensile strains, indicates a possible emergence of a spatially modulated incommensurate polar phase induced by the flexo-strain effects. Analytical results, derived in this work, open the way for flexo-strain engineering of soft phonon and ferron dispersion in thin films of van der Waals ferrielectrics.
发表机构
- Institute of Physics, National Academy of Sciences of Ukraine（乌克兰国家科学院物理研究所）
- Frantsevich Institute for Problems in Materials Science, National Academy of Sciences of Ukraine（乌克兰国家科学院弗拉采维奇材料科学问题研究所）
- Department of Materials Science and Engineering, University of Wisconsin-Madison（威斯康星大学麦迪逊分校材料科学与工程系）
- V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine（乌克兰国家科学院V.拉什卡廖夫半导体物理研究所）
- Department of Microelectronics, Igor Sikorsky Kyiv Polytechnic Institute（伊戈尔·西科尔斯基基辅理工学院微电子系）
- Institute of Solid-State Physics and Chemistry, Uzhhorod University（乌日霍罗德大学固体物理与化学研究所）
- Department of Materials Science and Engineering, Pennsylvania State University（宾夕法尼亚州立大学材料科学与工程系）
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