Nodal Line Topological Superconducting State in Quasi-One-Dimensional A2Cr3As3 (A = K, Rb, Cs) Superconductors

In this theoretical study, we examine the topological properties of the recently discovered A2Cr3As3 (A = K, Rb, Cs) superconductors. In the superconducting state, characterized by a typical $${{p}_{z}}$$ -wave pairing symmetry, a line nodal exists in the $${{k}_{z}} = 0$$ plane, confirming the system as a topological nodal-line superconductor. When considering an open boundary along the $$z$$ -direction, flat surface bands emerge. In contrast, when an s-wave pairing symmetry is considered, the system becomes fully gapped and topologically trivial. Additionally, we investigate the spectral function and the local density of states, which may be employed to experimentally detect the topological features.