Topological Dirac Nodal-Line Structure in Orthorhombic-Ti3N2

As a new type of titanium nitrides phase, orthorhombic-Ti3N2(o-Ti3N2) possesses coexistence oftime-reversal symmetry, spatial inversion symmetry, band inversion and negligible spin-orbit-coupling (SOC), hence it is expected to have special physical and chemical properties. In this work, its electronic and topological properties were systematically investigated by combing first-principles calculations and Wannier tight-binding analysis. It is found that o-Ti(3)N(2)is a 3D topological nodal-line material characterized by hornlike nodal lines in 3D momentum space. The "drumhead-like" surface states exist on the (001) surface, while surface states possess the exotic single-double conversion, implying that o-Ti3N2 may process interesting surface transport properties. These features make o-Ti3N2 a new member in topological materials, with promising novel applications in electronic devices.