Collective interlayer pairing and pair superfluidity in vertically stacked layers of dipolar excitons

Abstract

Layered bosonic dipolar fluids have been suggested to host a condensate of interlayer molecular bound states. However, its experimental observation has remained elusive. Motivated by two recent experimental works [Hubert et al., Phys. Rev. X 9, 021026 (2019) and D. J. Choksy et al., Phys. Rev. B 103 045126 (2021)], we theoretically study, using numerically exact quantum Monte Carlo calculations, the experimental signatures of collective interlayer pairing in vertically stacked indirect exciton (IX) layers. We find that IX energy shifts associated with each layer evolve non trivially as a function of density imbalance following a nonmonotonic trend with a jump discontinuity at density balance, identified with the interlayer IX molecule gap. This behavior discriminates between the superfluidity of interlayer bound pairs and independent dipole condensation in distinct layers. Considering finite temperature and finite density imbalance conditions, we find a cascade of Berezinskii--Kosterlitz--Thouless (BKT) transitions, initially into a pair superfluid and only then, at lower temperatures, into complete superfluidity of both layers. Our results may provide a theoretical interpretation of existing experimental observations in GaAs double quantum well (DQW) bilayer structures. Furthermore, to optimize the visibility of pairing dynamics in future studies, we present an analysis suggesting realistic experimental settings in GaAs and transition metal dichalcogenide (TMD) bilayer DQW heterostructures where collective interlayer pairing and pair superfluidity can be clearly observed.

Published version

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Cited by in corpus (8)

• Thickness mapping and layer number identification of exfoliated van der Waals materials by Fourier imaging micro-ellipsometry
• Collective interlayer pairing and pair superfluidity in vertically stacked layers of dipolar excitons
• Searching for Unconventional Superfluid in Excitons of Monolayer Semiconductors
• Edge modes in chiral electron double layers
• Electrically tunable and enhanced nonlinearity of moiré exciton-polaritons in transition metal dichalcogenide bilayers
• Nonlocal order parameter of pair superfluids
• Chiral Josephson effect in double layers: the role of particle-hole duality
• Trimer superfluidity of antiparallel dipolar excitons in a bilayer heterostructure