A doping-dependent switch from one- to two-component electron-hole superfluidity with high transition temperatures in coupled TMD monolayers.

Electron-hole (e-h) superfluidity in a Transition Metal Dichalcogenide heterostructure consisting of coupled MoSe₂-WSe₂ monolayers, is investigated using mean-field approach. We include self-consistent screening of the electron-hole interaction and the multibands effects arising from the strong spin-orbit band splitting [1].

The different magnitude of the valence and conduction band splitting results in a large energy misalignment of the electron and hole bands [2]. This misalignment is completely different if the doping of the monolayers is interchanged between MoSe₂(e)/WSe₂(h) and MoSe₂(h)/WSe₂(e), and depending on the choice of doping, the superfluidity may or may not be tuneable by density from one- to two-components. We find that only MoSe2(h)/WSe2(e) can have both one-component and two-component superfluidity.

The electron-hole pairing is much stronger than in graphene[3] due to the large effective masses so superfluidity is predicted for densities up to 10¹³ cm^-2. The transition temperatures are high, up to 100 K, which is consistent with a very recent experiment on the identical system[4].

[1] S. Conti et al, arXiv:1909.03411 (2019)
[2] K. Kosmider et al, Phys. Rev. B 88, 245436 (2013)
[3] S. Conti et al, Phys. Rev. B 99, 144517 (2019)
[4] Z. Wang et al Nature 574, 76 (2019)