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) Bi2S2Te because of its unique structure feature. In particular, the spin‐singlet spatially indirect excitons in Bi2S2Te 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 Bi2S2Te, 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 Bi2S2Te, respectively. It therefore can be confirmed that Bi2S2Te 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.