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Large family of two-dimensional ferroelectric metals discovered via machine learning
Science Bulletin ( IF 18.9 ) Pub Date : 2020-09-05 , DOI: 10.1016/j.scib.2020.09.010
Xing-Yu Ma 1 , Hou-Yi Lyu 2 , Kuan-Rong Hao 1 , Yi-Ming Zhao 3 , Xiaofeng Qian 4 , Qing-Bo Yan 3 , Gang Su 5
Affiliation  

Ferroelectricity and metallicity are usually believed not to coexist because conducting electrons would screen out static internal electric fields. In 1965, Anderson and Blount proposed the concept of “ferroelectric metal”, however, it is only until recently that very rare ferroelectric metals were reported. Here, by combining high-throughput ab initio calculations and data-driven machine learning method with new electronic orbital based descriptors, we systematically investigated a large family (2964) of two-dimensional (2D) bimetal phosphates, and discovered 60 stable ferroelectrics with out-of-plane polarization, including 16 ferroelectric metals and 44 ferroelectric semiconductors that contain seven multiferroics. The ferroelectricity origins from spontaneous symmetry breaking induced by the opposite displacements of bimetal atoms, and the full-d-orbital coinage metal elements cause larger displacements and polarization than other elements. For 2D ferroelectric metals, the odd electrons per unit cell without spin polarization may lead to a half-filled energy band around Fermi level and is responsible for the metallicity. It is revealed that the conducting electrons mainly move on a single-side surface of the 2D layer, while both the ionic and electric contributions to polarization come from the other side and are vertical to the above layer, thereby causing the coexistence of metallicity and ferroelectricity. Van der Waals heterostructures based on ferroelectric metals may enable the change of Schottky barrier height or the Schottky-Ohmic contact type and induce a dramatic change of their vertical transport properties. Our work greatly expands the family of 2D ferroelectric metals and will spur further exploration of 2D ferroelectric metals.



中文翻译:

通过机器学习发现的大型二维铁电金属家族

通常认为铁电性和金属性不会共存,因为传导电子会屏蔽静态内部电场。1965年Anderson和Blount提出了“铁电金属”的概念,但直到最近才报道了非常稀有的铁电金属。在这里,通过从头开始结合高通量基于新的电子轨道描述符的计算和数据驱动的机器学习方法,我们系统地研究了一个大家族(2964)的二维(2D)双金属磷酸盐,并发现了 60 个稳定的平面外极化铁电体,包括 16 个铁电体金属和 44 种铁电半导体,其中包含 7 种多铁性物质。铁电性起源于双金属原子的相反位移引起的自发对称性破缺,而全d-轨道铸币金属元素比其他元素引起更大的位移和极化。对于 2D 铁电金属,没有自旋极化的每个晶胞的奇数电子可能导致费米能级附近的半满能带,并决定金属丰度。结果表明,导电电子主要在二维层的单侧表面移动,而离子和电对极化的贡献均来自另一侧并垂直于上层,从而导致金属性和铁电性共存. 基于铁电金属的范德瓦尔斯异质结构可以改变肖特基势垒高度或肖特基欧姆接触类型,并引起其垂直传输特性的显着变化。

更新日期:2020-09-05
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