Deformation-Potential-Driven Photostriction in Layered Ferroelectrics
University of Arkansas（阿肯色大学）；Smart Ferroic Materials Center and Institute for Nanosciences & Engineering, University of Arkansas（阿肯色大学智能铁电材料中心与纳米科学与工程研究所）；Université Paris-Saclay, CentraleSupélec, CNRS, Laboratoire SPMS（巴黎-萨克雷大学、中央苏佩莱克学院、法国国家科学研究中心、SPMS实验室）；Tel Aviv University（特拉维夫大学）
S. Puri, R. Rodriguez, C. Dansou, L. Bouric, A. Sheibani, C. Paillard, L. Bellaiche, H. Nakamura
The coupling between electronic excitations and lattice deformation in van der Waals ferroelectrics is governed by a competition between the electron deformation potential and the inverse piezoelectric effect. While theory predicts that piezoelectric screening should drive a polar-axis contraction in monolayer group-IV monochalcogenides, we demonstrate that in multilayer SnS, the deformation potential provides the dominant contribution, driving a polar-axis expansion even within ferroelectric domains. By correlating polarization-resolved second-harmonic generation microscopy with ultrafast reflectance spectroscopy and first-principles calculations, we resolve the anisotropic lattice response and disentangle intrinsic photostrictive strain from extrinsic thin-film interference artifacts. These results establish a microscopic hierarchy of photostrictive mechanisms and position stacking-engineered SnS as a platform for ultrafast optomechanical transduction.
Giant photostriction in lead-free ferroelectric stemming from photo-excited thermalized carriers
Université Paris-Saclay, CentraleSupélec（巴黎萨克雷大学、中央理工-高等电力学院）；CNRS, Laboratoire SPMS（法国国家科学研究中心，SPMS实验室）；ENS Paris-Saclay（巴黎萨克雷高等师范学院）；LuMIn；Centre de Nanosciences et de Nanotechnologies (C2N)（纳米科学与工程中心）；Le Mans Université（勒芒大学）；Institut des Molécules et Matériaux du Mans（勒芒分子与材料研究所）；FZU- Institute of Physics, Czech Academy of Sciences（捷克科学院物理研究所）
Anisotropic Photostriction and Strain-modulated Carrier Lifetimes in Orthorhombic Semiconductors
National Center for Nanoscience and Technology, Chinese Academy of Sciences（中国科学院国家纳米科学中心）；Institute of Physics, Chinese Academy of Sciences（中国科学院物理研究所）；Songshan Lake Materials Laboratory（松山湖材料实验室）
Copper indium thiophosphate, CuInP2S6, has attracted much attention in recent years due to its van der Waals layered structure and robust ferroelectricity at room temperature. In this review, we aim to give an overview of the various properties of CuInP2S6, covering structural, ferroelectric, dielectric, piezoelectric and transport properties, as well as its potential applications. We also highlight the remaining questions and possible research directions related to this fascinating material and other compounds of the same family.
Bulk photovoltaic effect enhancement via electrostatic control in layered ferroelectrics
铁电钙钛矿氧化物的体光伏效应（BPVE）的漂移电流机制与结构和电子性质之间的关系还没有得到很好的理解。本文从第一性原理出发，研究了具有可见光吸收的铁电体Pb（Ni $_{x}$ Ti $_{1-x}$）O $_{3-x}$固溶体的位移电流光伏效应。我们发现，共价轨道字符指示的方向，幅度和起始能量的移位电流在一个可预测的方式。特别是，我们发现，移位电流响应可以通过在层状铁电体中的静电控制来增强，因为束缚电荷面临更强的动力来屏蔽较厚材料中的电场，使电子密度离域。这种具有交替光电流产生层和绝缘层的异质分层结构是BPVE应用的理想选择。
Doping ferroelectrics with carriers is often detrimental to polarization. This makes the design and discovery of metals that undergo a ferroelectric-like transition challenging. In this letter, we show from first principles that the oxygen octahedral rotations in perovskites are often enhanced by electron doping, and this can be used as a means to strengthen the structural polarization in certain hybrid-improper ferroelectrics -- compounds in which the polarization is not stabilized by the long range Coulomb interactions but is instead induced by a trilinear coupling to octahedral rotations. W…
The van der Waals layered material CuInP2S6 features interesting functional behavior, including the existence of four uniaxial polarization states, polarization reversal against the electric field through Cu ion migration, a negative-capacitance regime, and reversible extraction of Cu ions. At the heart of these characteristics lies the high mobility of Cu ions, which also determines the spontaneous polarization. Therefore, Cu migration across the lattice results in unusual ferroelectric behavior. Here, we demonstrate how the interplay of polar and ionic properties provides a path to ionically…
Origin and evolution of ferroelectricity in the layered rare-earth-titanate, $R_2$Ti$_2$O$_{7}$, Lichtenberg phases
我们报告了一个系统的第一性原理研究的基础上的密度泛函理论（DFT）的结构和铁电性能的$R_2$ Ti $_2$ O $_{7}$钙钛矿相关的氧化物与$R=$ La，Ce，Pr和Nd。我们发现，在所有情况下，铁电体扭曲的基态极性$P2_1$结构从其母中心对称的$P2_1/m$阶段是由一个单一的极性软模式组成的旋转和倾斜的TiO $_6$八面体结合的$R$离子的位移驱动。二次中心对称畸变，这是稳定的母体结构，大大有助于降低基态的能量。我们评估了整个系列的结构和极化的趋势作为PDMATHAMT的函数，并调和了文献中报道的极化值的差异。我们的结果证实了$R_2$ Ti $_2$ O $_{7}$材料家族属于适当几何铁电体类。
Origin of the phase change from pyrochlore to perovskite-like layered structure and a new lead free ferroelectric
以A2 B2 O 7为化学式的材料是一个著名的家族，有300多种化合物，具有丰富的性质，如铁电、多铁性和光催化性能等。一般来说，这一家族主要有两种结构，即烧绿石和类钙钛矿层状（PL）结构。以前，这些材料的结构和性能设计通常是复杂的，并且是固溶体，这使得制造复杂化，并且在性能的微观起源的研究中引入复杂性。本文报道了纯Eu_2Ti_2O_7在高温高压下发生的焦绿石-PL结构的变化，并且所形成的PL结构将通过加热而转移回来。这些结果表明，PL-烧绿石固溶体中形成的PL结构是由于纯烧绿石化合物中高压形成的PL结构调节到环境压力。这些结果表明，高压和高温可以用来操纵从烧绿石到PL结构的晶体结构，反之亦然。此外，PL Eu_2Ti_2O_7首次被确认为无铅铁电材料。
Realization of large and highly tunable second-order nonlinear optical (NLO) responses, e.g., second-harmonic generation (SHG) and bulk photovoltaic effect (BPVE), is critical for developing modern optical and optoelectronic devices. Very recently, the two-dimensional van der Waals ferroelectric NbOX2 (X = Cl, Br or I) are discovered to exhibit unusually large and anisotropic SHG. However, the physical origin and possible tunability of NLO responses in NbOX2 remain to be unclear. In this article, we reveal that the large SHG in NbOCl2 is dominated by the synergy between large transition dipole…
Ferromagnetism and orbital order in a topological ferroelectric
我们探索通过密度泛函计算的磁性掺杂的拓扑铁电体作为一种非常规的路线，多铁性。层状钙钛矿La $_{2}$ Ti $_{2}$ O $_{7}$的钒掺杂在很大程度上保持了电极化的强度并产生了稳健的铁磁有序性，因此具有适当的多铁性。掺杂剂聚集成链的显著趋势导致在一般掺杂下的绝缘特性。铁磁性源于多轨道V系统通过不寻常的“反铁”轨道顺序的对称性破缺，以及宿主的低对称性层状结构。
Recently, a layered ferroelectric CuInP2Se6 was shown to exhibit domain walls with locally enhanced piezoresponse - a striking departure from the observations of nominally zero piezoresponse in most ferroelectrics. Although it was proposed that such "bright" domain walls are phase-boundaries between ferri- and antiferroelectrically ordered regions of the materials, the physical mechanisms behind the existence and response of these boundaries remain to be understood. Here, using Landau-Ginzburg-Devonshire phenomenology combined with four sub-lattices model, we describe quantitatively the bright…
High-mobility layered semiconductors have the potential to enable the next-generation electronics and computing. This paper demonstrates that the ultrahigh electron mobility observed in the layered semiconductor Bi$_2$O$_2$Se originates from an incipient ferroelectric transition that endows the material with a robust protection against mobility degradation by Coulomb scattering. Based on first-principles calculations of electron-phonon interaction and ionized impurity scattering, it is shown that the electron mobility of Bi$_2$O$_2$Se can reach 10$^4$ to 10$^6$ cm$^2$V$^{-1}$s$^{-1}$ over a wi…
2D layered ferroelectric materials such as CuInP$_2$S6 (CIPS) are promising candidates for novel and high-performance photocatalysts, owning to their ultrathin layer thickness, strong interlayer coupling, and intrinsic spontaneous polarization, while how to control the photocatalytic activity in layered CIPS remains unexplored. In this work, we report for the first time the photocatalytic activity of ferroelectric CIPS for the chemical deposition of silver nanostructures (AgNSs). The results show that the shape and spatial distribution of AgNSs on CIPS are tunable by controlling layer thicknes…
Several families of layered perovskite oxide ferroelectrics exhibit a coupling between polarization and structural order parameters, such as octahedral rotation distortions. This coupling provides opportunities for novel electric field-based manipulation of material properties, and also stabilizes complex domain patterns and domain wall vortices. Amongst layered perovskites with such coupled orders, the Aurivillius-phase oxides SrBi$_2B_2$O$_9$ ($B$=Ta, Nb) are well-known for their excellent room temperature ferroelectric performance. This work combines group theoretic analysis with density fu…
Magnetic field driven enhanced ferroelectric switching in self-grown ferroelectric-ferromagnetic composite in the BiFeO3-BaTiO3 multiferroic alloy system
多年来，人们试图弥补多铁性BiFeO 3体相态的固有弱点，如高漏电流和铁磁相关性的缺乏，并通过与其他钙钛矿形成固溶体来利用其磁电势。近几年的研究表明，BiFeO_3与BaTiO_3的合金化，无论有无添加剂，都可以诱导铁电和铁磁开关。虽然从技术应用的角度来看，这两种铁性序的共存是令人鼓舞的，但该系统中铁磁性的起源仍然难以捉摸。在这里，我们合成了这样的组合物，并进行了详细的结构分析，采用磁性分离的粉末颗粒。我们发现，铁磁性的起源在于自发沉淀的一个小的（~ 1wt%）钡六角铁氧体（BaFe 9 O 19）相，通常未检测到在常规的X射线衍射研究从整个标本的粉末取样。我们还表明，尽管微不足道的分数的亚铁磁相，这种自生长的复合材料表现出显着增强的铁电开关在外部磁场的存在下。我们得到了一个直流磁电耦合~ 9 × 10-8 s/m，这是一个值，这是已报道的层状铁电/铁磁层压板和双层薄膜铁电-铁磁hetrostructures。我们的研究表明，合理的大磁电耦合是可实现的，在简单的0-3铁电-铁磁块状复合材料提供的合成策略的开发，诱导自发沉淀的铁磁相在小体积分数，以确保良好的绝缘行为的复合材料，从而开发。
Using high-throughput first-principles calculations to search for layered van der Waals materials with the largest piezoelectric stress coefficients, we discover NbOI2 to be the one among 2940 monolayers screened. The piezoelectric performance of NbOI2 is independent of thickness, and its electromechanical coupling factor of near unity is a hallmark of optimal interconversion between electrical and mechanical energy. Laser scanning vibrometer studies on bulk and few-layer NbOI2 crystals verify their huge piezoelectric responses, which exceed internal references such as In2Se3 and CuInP2S6. Fur…
Turning ABO$_3$ antiferroelectrics into ferroelectrics: Design rules for practical rotation-driven ferroelectricity in double perovskites and A$_3$B$_2$O$_7$ Ruddlesden-Popper compounds
Direct observation of ferroelectricity in Ca$_3$Mn$_2$O$_7$ and its prominent light absorption
已知层状钙钛矿$A_3M_2$ O $_7$表现出所谓的混合反常铁电性。尽管实验证实的情况下（例如，$M$ =Ti和Sn），铁电性在磁性Ca $_3$ Mn $_2$ O $_7$仍然是一个谜。在这里，结构，铁电，磁电和光学性能的钙$_3$锰$_2$ O $_7$进行了系统的研究。可切换的极化直接测量，证明其铁电性。此外，还发现了磁电响应，暗示了磁性和铁电性之间的耦合。此外，观察到强的可见光吸收，这可以从其电子结构理解。其直接和适当的带隙，以及宽的导电带，使钙$_3$锰$_2$ O $_7$的铁电光电应用的潜在候选人。
Quadratic piezoelectricity from stacking-engineered interference in multilayer sliding ferroelectrics
Inner Mongolia University（内蒙古大学）；Nanjing University（南京大学）；Institute of Metal Research, Chinese Academy of Sciences（中国科学院金属研究所）；University of Science and Technology of China（中国科学技术大学）
Aluminum nitride is piezoelectric and exhibits spontaneous polarization along the $c$-axis, but the polarization cannot be switched by applying an electric field. Adding Sc to AlN enhances the piezoelectric properties, and can make the alloy ferroelectric. We perform a detailed first-principles analysis of spontaneous and piezoelectric polarization. Comparisons between explicit supercell calculations show that the virtual crystal approximation produces accurate results for polarization, but falls short in describing the phase stability of the alloy. We relate the behavior of the piezoelectric …
