First-Principles Study Reveals an Electronic Correlation Effect on the Topological and Electronic Properties of Janus RuClF Monolayers: Implications for Spintronics and Valleytronics Applications

Combining the nontrivial band topology with the intrinsic ferrovalley (FV), the valley-nonequilibrium quantum anomalous Hall effect (VQAHE) attracts growing attention both for its potential applications and basic physics. The electronic properties of some systems with localized orbital distribution and special structures could be influenced by the electronic correlation effect. In our work, the electronic correlation effect on the electronic structures for a Janus RuClF monolayer (ML) is investigated based on the first-principles calculations + U method. For the magnetization orientation along the out-of-plane (OOP) direction, RuClF ML undergoes FV to half-valley-metal (HVM) to VQAHE to HVM to FV transitions with increasing electron correlation effects. There is a chiral edge state connecting the valence and conduction bands and an integer Chern number (C = 1) when 2.52 < U < 2.55 eV. No obvious valley polarization and special VQAHE phases occur for the magnetization orientation along the in-plane (IP) direction. Regardless of IP or OOP magnetic anisotropy, the sign-reversible Berry curvature can be found with increasing U values. Notably, with increasing U values, the magnetization of RuClF ML varies from OOP to IP, and the key U value is approximately 2.41 eV. When taking into account the intrinsic magnetic anisotropy, no HVM and VQAHE states exist. This work finds the significance of magnetic anisotropy and electronic correlation effects in RuClF ML and highlights that electronic correlation effects can induce unusual topological phase transitions. Our consequences manifest that RuClF ML is an admirable material for topological electronic, spintronic, and valleytronic applications.