Chern insulators and high Curie temperature Dirac half-metal in two-dimensional metal–organic frameworks

Abstract

Two-dimensional (2D) magnetic materials with nontrivial topological states have recently drawn considerable attention. Among them, 2D metal-organic frameworks (MOFs) are standing out due to their advantages such as the easy synthesis in practice and less sensitivity to oxidation that are distinctly different from inorganic materials. By means of density-functional theory calculations, we systematically investigate the electronic and topological properties of a class of 2D MOFs X(C21H15N3) (X = transition metal element from 3 d to 5 d). Excitingly, we find that X(C21H15N3) (X = Ti, Zr, Ag, Au) are Chern insulators with sizable band gaps (∼7.1 meV). By studying a four-band effective model, it is revealed that the Chern insulator phase in X(C21H15N3) (X = Ti, Zr, Ag, Au) is caused cooperatively by the band inversion of the p orbitals of the C21H15N3 molecule and the intrinsic ferromagnetism of X(C21H15N3). Additionally, Mn(C21H15N3) is a Dirac half-metal ferromagnet with a high Curie temperature up to 156 K. Our work demonstrates that 2D MOFs X(C21H15N3) are good platforms for realizing the quantum anomalous Hall effect and designing spintronic devices based on half-metals with high-speed and long-distance spin transport.

Magnetization direction-controlled topological band structure in TlTiX (X = Si, Ge) monolayers

“…Hence, achieving the QAH effect has become an exceedingly significant focal point within the realm of condensed matter physics. To date, several realistic QAH insulators have been successively predicted by theoretical calculations and confirmed by multiple experimental techniques such as angleresolved photoemission spectroscopy and electrical transport measurements [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24]. The first observation of the QAH effect occurred in thin films of (Bi; Sb) 2 Te 3 doped with Cr at extremely low temperatures (below 30 mK) due to the weak magnetic coupling in the doped Cr atoms and the narrow band gap of the material [25].…”

Genuine Dirac Half‐Metals in Two‐Dimensions

“…[13][14][15] More interestingly, the link between magnetism and band topology in the 2D family has become a popular study topic. [16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34] As indicated in Table S1 (Supporting Information), we reviewed a series of published literature and discovered that many researchers have proposed 2D half-metals (or 2D spin-gapless semiconductors) with linearly dispersed crossing points. We would like to indicate that all the linearly dispersed crossing points with twofold degeneracy proposed in the reviewed literature (see Table S1, Supporting Information) are classified as "Dirac points".…”