He Chaoyu, Liao Yujie, Ouyang Tao, Zhang Huimin, Xiang Hongjun, Zhong Jianxin
Laboratory for Quantum Engineering and Micro-Nano Energy Technology and School of Physics and Optoelectronics, Xiangtan University, Xiangtan 411105, China.
Key Laboratory of Computational Physical Sciences (Ministry of Education), Institute of Computational Physical Sciences, Department of Physics, Fudan University, Shanghai 200433, China.
Fundam Res. 2023 Dec 17;5(1):138-144. doi: 10.1016/j.fmre.2023.12.001. eCollection 2025 Jan.
Half-filled isolated flat-band paves a new way to realize high-temperature ferromagnetic semiconductor for spintronics applications, but it is extremely rare in lattice models and lacking in realistic materials. Herein, the 2 × 2 super-cell of the honeycomb lattice with a single-hole defect is proposed as a new lattice model (HL-D-1/8) to realize nontrivial isolated flat-bands. We further demonstrate that CN monolayer of the experimentally realized graphitic carbon nitride (Adv. Mater., 22, 1004, 2010; Nat. Commun., 9, 3366, 2018) is a perfect system holding such a lattice to host flat-bands. A new corrugated Pca21 configuration is proposed as the ground state for the free-standing CN monolayer, which is dynamically stable and energetically more favorable than the widely-used flat one without dynamical stability. The Pca21 configuration is found to be an intrinsic ferromagnetic half-semiconductor ( ≈ 241 K) with one semiconducting spin-channel (1.75 eV) and one insulating spin-channel (3.64 eV), which is quite rare in two-dimensional systems. Its ferromagnetic semiconducting property originates from the isolated -state flat-band as the corrugation shifts the flat-band upward to the Fermi level. Interestingly, such a corrugated Pca21 CN monolayer is found to be both piezoelectric and ferroelectric, which makes it an unusual metal-free two-dimensional multiferroic.
半填充孤立平带为自旋电子学应用中实现高温铁磁半导体开辟了一条新途径，但在晶格模型中极为罕见，且现实材料中也不存在。在此，提出具有单孔缺陷的蜂窝晶格2×2超胞作为一种新的晶格模型（HL-D-1/8）以实现非平凡孤立平带。我们进一步证明，实验实现的石墨相氮化碳（《先进材料》，22, 1004, 2010；《自然通讯》，9, 3366, 2018）的CN单层是拥有这种晶格以承载平带的完美体系。提出一种新的波纹状Pca21构型作为独立CN单层的基态，它动态稳定且在能量上比广泛使用的无动态稳定性的平构型更有利。发现Pca21构型是一种本征铁磁半半导体（居里温度≈241 K），具有一个半导体自旋通道（1.75 eV）和一个绝缘自旋通道（3.64 eV），这在二维体系中相当罕见。其铁磁半导体性质源于孤立的π态平带，因为波纹使平带向上移动到费米能级。有趣的是，发现这种波纹状Pca21 CN单层兼具压电性和铁电性，这使其成为一种非同寻常的无金属二维多铁性材料。
Zotero 插件
