Anisotropy-induced phase transitions in an intrinsic half-Chern insulator NiI

• Published in: Nanoscale Vol. 14; no. 36; pp. 13378 - 13388
• Main Authors: Liu, Lei, Huan, Hao, Xue, Yang, Bao, Hairui, Yang, Zhongqin
• Format: Journal Article
• Published: 22.09.2022
• ISSN: 2040-3364; 2040-3372
• DOI: 10.1039/d2nr02599j

One crucial target of research on spintronics is to achieve flexibly tunable and highly efficient spin-polarized electronic current. In this work, by using first-principles calculations and topological characterization theories, we propose an intrinsic half-Chern insulator (HCI) in a Ni 2 I 2 monolayer, which possesses 100% spin-polarized topologically nontrivial edge states, distinct from ordinary Chern insulators. Its band gap is formed due to the lifting of the double degeneracy of non-Dirac bands composed of Ni d xz /d yz orbitals. The HCI becomes a half semiconductor (HS) or a combined state of a half metal (HM) and an HCI if biaxial strain is applied. The phase transition is found to be associated with the unique anisotropy of the bands, originating from the diverse orbital distributions and the opposite moving in energy of Ni d xy and d xz /d yz bands under the strain. Our findings demonstrate that the monolayer Ni 2 I 2 is a unique Chern insulator with ideal spintronic properties, supporting versatile applications in spintronic devices with very high spin polarization and extremely low-power dissipation. An intrinsic half-Chern insulator, possessing 100% spin-polarized edge states, is found in Ni 2 I 2 monolayers. A combined state of a half metal and a half-Chern insulator occurs in the material under strain, associated with the unique anisotropic bands.