High‐Temperature Excitonic Condensation in 2D Lattice

Abstract Exploration of high‐temperature bosonic condensation is of significant importance for the fundamental many‐body physics and applications in nanodevices, which, however, remains a huge challenge. Here, in combination of many‐body perturbation theory and first‐principles calculations, a new‐type spatially indirect exciton can be optically generated in two‐dimensional (2D) Bi 2 S 2 Te because of its unique structure feature. In particular, the spin‐singlet spatially indirect excitons in Bi 2 S 2 Te monolayer are dipole/parity allowed and reveal befitting characteristics for excitonic condensation, such as small effective mass and satisfied dilute limitation. Based on the layered Bi 2 S 2 Te, the possibility of the high‐temperature excitonic Bose–Einstein condensation (BEC) and superfluid state in two dimensions, which goes beyond the current paradigms in both experiment and theory, are proved. It should be highlighted that record‐high phase transition temperatures of 289.7 and 72.4 K can be theoretically predicted for the excitonic BEC and superfluidity in the atomic thin Bi 2 S 2 Te, respectively. It therefore can be confirmed that Bi 2 S 2 Te featuring bound bosonic states is a fascinating 2D platform for exploring the high‐temperature excitonic condensation and applications in such as quantum computing and dissipationless nanodevices.