Emergence of topological and spin valley hallmarks in buckled Xene bilayers

A subclass of two-dimensional materials with honeycomb structure, namely buckled Xene monolayers, are efficient for topological applications due to varying degrees of buckling in their lattice structure and have received a significant revival of interest in the last few years. However, to-date, less attention, as compared to, planer Xene bilayers has been assigned to the buckled Xene bilayers. The buckled Xene bilayers can offer a unique platform to study transport properties in bilayer systems. In this study, we explore the unknown topological behaviour of buckled Xene bilayers by exploiting the space inversion and time-reversal (TR) symmetries in these solids. In order to exploit the underline symmetries, we use light irradiation, layered antiferromagnetic exchange magnetization and vertical electric field as an external means. By mixing these three ingredients in a proper way, we achieve various topological phases in bilayers of buckled Xene solids, including TR-broken quantum spin Hall insulator, photo-induced quantum Hall insulator, photo-induced spin-polarized quantum Hall insulator, and quantum spin-valley Hall insulator. Furthermore, we establish a topological phase diagram and identify a topological domain wall in buckled Xene bilayers when subjected to circularly polarized light and gated voltage, which opens up possibilities for the propagation of perfectly valley-polarized channels.