Key role of the moire potential for the quasi-condensation of interlayer excitons in van der Waals heterostructures

TL;DR

This paper investigates how the moire potential in TMD bilayers influences interlayer exciton behavior, revealing conditions for exciton superfluidity at low temperatures and the emergence of a finite-momentum quasi-condensate.

Contribution

It demonstrates that the moire potential significantly increases exciton effective mass and enables superfluidity at accessible temperatures with specific dielectric engineering.

Findings

Moire potential causes exponential increase in exciton effective mass.

Superfluidity can occur below approximately 10 K with proper dielectric layers.

Interlayer excitons form a finite-momentum quasi-condensate that is optically inactive.

Abstract

Interlayer excitons confined in bilayer heterostructures of transition metal dichalcogenides (TMDs) offer a promising route to implement two-dimensional dipolar superfluids. Here, we study the experimental conditions necessary for the realisation of such collective state. Particularly, we show that the moire potential inherent to TMD bilayers yields an exponential increase of the excitons effective mass. To allow for exciton superfluidity at sizeable temperatures it is then necessary to intercalate a high-$\kappa$ dielectric between the monolayers confining electrons and holes. Thus the moire lattice depth is sufficiently weak for a superfluid phase to theoretically emerge below a critical temperature of around 10 K. Importantly, for realistic experimental parameters interlayer excitons quasi-condense in a state with finite momentum, so that the superfluid is optically inactive and flows spontaneously.