KTlO: A metal shrouded 2D semiconductor with high carrier mobility and tunable magnetism

Two-dimensional (2D) materials with high carrier mobility and tunable magnetism are in high demand for nanoelectronics and spintronic applications. Herein, we predict a novel two-dimensional monolayer KTlO that possesses an indirect band gap of 2.25 eV (based on HSE06) and high carrier mobility (1860 $\mathrm{cm^2\ V^{-1}s^{-1}}$ for electron and 2540 $\mathrm{cm^2\ V^{-1}s^{-1}}$ for hole) by means of ab initio calculations. KTlO monolayer has a calculated cleavage energy of 0.56 $\mathrm{J\ m^{-2}}$, which suggests exfoliation of bulk material as viable means for the preparation of mono- and few-layer materials. Remarkably, the KTlO monolayer suggests tunable magnetism and half-metallicity with hole doping, which are attributed to the novel Mexican-hat-like bands and van Hove singularities in its electron structure. Furthermore, monolayer KTlO exhibits moderate optical absorption over visible light and ultraviolet region. The band gap value and band characteristics of monolayer KTlO can be strongly manipulated by biaxial and uniaxial strains to meet the requirements of various applications. All these novel properties render monolayer KTlO a promising functional material for future nanoelectronics and spintronic applications.