Monolayer Cr2Ge2Te6 (ML-CGT) has attracted broad interest due to its novel electronic and magnetic properties. However, there are still controversies on the origin of its intrinsic magnetism. Here, we systematically...

Two-dimensional (2D) materials with Nodal line band crossing have been attracting great research interest. However, it remains a challenge to find high-stable Nodal line structure in 2D systems. Herein, based on first-principles calculations and theoretical analysis, we propose that monolayer B6O possesses symmetry protected Dirac nodal line (DNL) state, with its Fermi velocity of 106 m/s in the same order of magnitude as that of graphene. The origin of DNL fermions is induced by coexistence of time-reversal symmetry and inversion symmetry. A two-band tight-binding model is further given to understand the mechanism of DNL. Considering its robustness against SOC and high structural stability, these results suggest monolayer B6O as a new platform for realizing future high-speed low-dissipation devices.