Two-dimensional (2D) honeycomb-like materials have been widely studied due to their fascinating properties. In particular, 2D honeycomb-like transition metal monolayers, which are good 2D ferromagnet candidates, have attracted intense research interest. The honeycomb-like structure of hafnium, hafnene, has been successfully fabricated on the Ir(111) substrate. However, its electronic structure has not yet been directly elucidated. Here, we report the electronic structure of hafnene grown on the Ir(111) substrate using angle-resolved photoemission spectroscopy (ARPES). Our results indicate that the presence of spin-orbit coupling and Hubbard interaction suppresses the earlier predicted Dirac cones at the K points of the Brillouin zone. The observed band structure of hafnene near the Fermi level is very simple: an electron pocket centered at the Γ point of the Brillouin zone. This electron pocket shows typical parabolic dispersion, and its estimated electron effective mass and electron density are approximately 1.8 m_e and 7 × 10¹⁴ cm⁻², respectively. Our results demonstrate the existence of 2D electron gas in hafnene grown on the Ir(111) substrate and therefore provide key information for potential hafnene-based device applications.

Two-dimensional (2D) magnetic crystals have been extensively explored thanks to their potential applications in spintronics, valleytronics, and topological superconductivity. Here we report a novel monolayer magnet, namely puckered pentagonal VTe₂ (PP-VTe₂), intriguing atomic and electronic structures of which were firmly validated from first-principles calculations. The PP-VTe₂ exhibits strong intrinsic ferromagnetism and semiconducting property distinct from the half-metallic bulk pyrite VTe₂ (BP-VTe₂) phase. An unusual magnetic anisotropy with large magnetic exchange energies is found. More interestingly, the multiferroic coupling between its 2D ferroelasticity and in-plane magnetization is further identified in PP-VTe₂, lending it unprecedented controllability with external strains and electric fields. Serving as an emergent 2D ferromagnetic semiconductor with a novel crystal structure, monolayer PP-VTe₂ provides an ideal platform for exploring exotic crystalline and spin configurations in low-dimensional systems.