Three-dimensional electron-hole superfluidity in a superlattice close to room temperature

Bound pairs of electrons and holes in semiconductors may condense into a superfluid. The electron-hole coupling is predicted to be much stronger than in conventional superconductors when the electrons and holes are confined in separated layers.
Although there is strong theoretical and experimental evidence for electron-hole superfluidity in bilayer systems [1-4], the 2D superfluid transition is topological and the transition temperature is limited by strong 2D fluctuations and Kosterlitz-Thouless effects.
We show this limitation can be overcome and that high-temperature superfluidity can be generated in a 3D superlattice of alternating electron-doped and hole-doped monolayers.
The transition temperatures are not topological and can approach room temperature when the superfluid gaps are very large. As a quantitative example, we present results for an electron-hole superfluid in a superlattice of transition metal dichalcogenide monolayers in which the critical temperature can reach 270 K [5].

[1] A. Perali et al. Phys. Rev. Lett. 110, 146803 (2013)
[2] G. W. Burg et al. Phys. Rev. Lett. 120, 177702 (2018)
[3] Z. Wang et al. Nature 574, 76 (2019)
[4] A. Chaves and D. Neilson, Nature 574, 39 (2019)
[5] M. Van der Donck et al. Phys. Rev. B 102, 060503(R) (2020)