镧系元素氧端接二维碳化物的铁电性
Ferroelectricity in oxygen-terminated 2D carbides of lanthanide elements
AI总结：
本研究通过ab initio计算发现镧系元素氧端接二维碳化物M2CO2具有铁电和反铁电相，且双轴应变可调控其极化和带隙，展现出优异的紫外光吸收特性。
摘要：
我们研究了组成为M2CO2（M=Gd, Tb, Dy）的镧系元素氧功能化碳化物，它们形成二维（2D）结构。我们的ab initio计算表明，氧端接使M2C单层转变为具有两个动态稳定相的半导体。其中，能量有利的alpha相变为铁电相，而beta相变为反铁电相。施加面内双轴应变可将一相转变为另一相，以线性方式改变alpha相的铁电极化，并将基本带隙的大小和性质从直接变为间接。具有直接带隙的结构表现出面内各向同性的电子和光学性质。这类此前未被探索的系统在紫外范围内也表现出优异的光子吸收。
英文摘要：
We investigate the properties of oxygen-functionalized carbides of lanthanide elements with the composition M2CO2 (M=Gd, Tb,Dy) that form two-dimensional (2D) structures. Our ab initio calculations reveal that oxygen termination turns M2C monolayers into semiconductors with two dynamically stable phases. Of these, the energetically favored alpha-phase becomes ferroelectric, whereas the beta-phase turns anti-ferroelectric. Applying in-plane biaxial strain may transform one phase into the other, changes the ferroelectric polarization of the alpha-phase in a linear fashion, and modifies the size and nature of the fundamental band gap from direct to indirect. The structure with a direct band gap exhibits in-plane isotropic electronic and optical properties. This previously unexplored class of systems also exhibits excellent photon absorption in the ultraviolet range.
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