Sufficiency of exciton–exciton repulsion for mechanical stability in bilayer TMD Bose–Fermi mixtures

Determine whether the repulsive interaction between interlayer excitons in bilayer transition metal dichalcogenide heterostructures is sufficiently strong to ensure the mechanical stability of a two-dimensional Bose–Fermi mixture where tightly bound interlayer excitons act as bosons and doped charge carriers act as fermions, under experimentally relevant densities and parameters.

Background

The paper discusses the relevance of its results to Bose–Fermi mixtures realized in atomically thin semiconductors, where tightly bound excitons constitute the bosonic component and doped charge carriers constitute the fermionic component. Mechanical stability of such mixtures generally requires a repulsive boson–boson interaction, which, in the atomic gas context, is modeled as a weak short-range repulsion to prevent collapse.

For transition metal dichalcogenide (TMD) bilayers with interlayer excitons, the exciton dipole moments are expected to be aligned, leading to repulsive exciton–exciton interactions. However, the authors note that the magnitude of this repulsion may be small due to the tightly bound nature of excitons. They explicitly state uncertainty about whether this repulsion suffices to guarantee mechanical stability in realistic conditions, motivating a concrete open question about the viability of such solid-state Bose–Fermi mixtures.