Li Xiangyang, Liu Qing-Bo, Tang Yongsen, Li Wei, Ding Ning, Liu Zhao, Fu Hua-Hua, Dong Shuai, Li Xingxing, Yang Jinlong
Hefei National Research Center for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui 230026, China.
School of Materials Science and Engineering, Anhui University, Hefei, Anhui 230601, China.
J Am Chem Soc. 2023 Apr 12;145(14):7869-7878. doi: 10.1021/jacs.2c12780. Epub 2023 Mar 16.
Two-dimensional (2D) semiconductors (SCs) integrated with two or more functions are the cornerstone for constructing multifunctional nanodevices but remain largely limited. Here, by tuning the spin state of organic linkers and the symmetry/topology of crystal lattices, we predict a class of unprecedented multifunctional SCs in 2D Cr(II) five-membered heterocyclic metal organic frameworks that simultaneously possess auxetic effect, room-temperature ferrimagnetism, chiral ferroelectricity (FE), electrically reversible spin polarization, and topological nodal lines/points. Taking 2D Cr(TDZ) (TDZ = 1.2.5-thiadiazole) as an exemplification, the auxetic effect is produced by the antitetra-chiral lattice structure. The high temperature ferrimagnetism originates from the strong - direct magnetic exchange interaction between Cr cations and TDZ doublet radical anions. Meanwhile, the clockwise-counterclockwise alignment of TDZ's dipoles results in unique 2D chiral FE with atomic-scale vortex-antivortex states. 2D Cr(TDZ) is an intrinsic bipolar magnetic SC where half-metallic conduction with switchable spin-polarization direction can be induced by applying a gate voltage. In addition, the symmetry of the little group of the lattice structure endows 2D Cr(TDZ) with topological nodal lines and a quadratic nodal point in the Brillouin zone near the Fermi level.
集成了两种或更多功能的二维（2D）半导体是构建多功能纳米器件的基石，但目前仍受到很大限制。在此，通过调节有机连接体的自旋态以及晶格的对称性/拓扑结构，我们预测了一类前所未有的二维Cr（II）五元杂环金属有机框架中的多功能半导体，它们同时具有负泊松比效应、室温亚铁磁性、手性铁电性（FE）、电可逆自旋极化以及拓扑节线/节点。以二维Cr（TDZ）（TDZ = 1,2,5 - 噻二唑）为例，负泊松比效应由反四面体手性晶格结构产生。高温亚铁磁性源于Cr阳离子与TDZ双自由基阴离子之间强烈的直接磁交换相互作用。同时，TDZ偶极子的顺时针 - 逆时针排列导致具有原子尺度涡旋 - 反涡旋态的独特二维手性铁电性。二维Cr（TDZ）是一种本征双极磁性半导体，通过施加栅极电压可诱导出具有可切换自旋极化方向的半金属传导。此外，晶格结构的小子群对称性赋予二维Cr（TDZ）在费米能级附近的布里渊区具有拓扑节线和一个二次节点。
