Spin–orbit stable dirac nodal line in monolayer B_(6)O

The 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 the first-principles calculations and theoretical analysis, we propose that monolayer B_(6)O possesses symmetry protected Dirac nodal line(DNL)state, with its Fermi velocity of 10^(6)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 spin–orbit coupling(SOC) and high structural stability, these results suggest monolayer B_(6)O as a new platform for realizing future high-speed low-dissipation devices.