Quadrupolar and dipolar phases of excitons in transition-metal dichalcogenide trilayer heterostructures

Abstract

Recent experiments on trilayer transition-metal dichalcogenide heterostructures have revealed the rich behavior of dipolar excitons. Motivated by these experimental observations, we investigate the collective dynamics of planar quantum dipoles whose orientations fluctuate because of charge tunneling between the outer layers. Using large-scale quantum Monte Carlo simulations, we map out the low-temperature phase diagram as a function of experimentally tunable parameters. We uncover a diverse landscape of phases driven by dipolar correlations. Under strong dipole fluctuations, a quadrupolar superfluid emerges. Suppressing charge tunneling nucleates a droplet state stabilized by the attractive interaction between antiparallel dipoles. At high exciton densities, the system gives way to a partially fragmented condensate, characterized by a finite interaction-driven occupation of the two dipolar states alongside a dominant quadrupolar superfluid component. Furthermore, exploring large effective masses that suppress zero-point motion, we find a staggered dipolar crystal at high densities. Our detailed study of the dependence of exciton energy shifts on an external electric field provides qualitative theoretical guidance for interpreting existing data, underscoring the crucial role of the antiparallel dipolar configuration and paving the way for future experimental explorations of quantum phases of trilayer excitons.