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

TL;DR

This paper explores the complex quantum phases of excitons in trilayer transition-metal dichalcogenides, revealing new superfluid, droplet, and crystal states driven by dipolar interactions and fluctuations, supported by large-scale quantum Monte Carlo simulations.

Contribution

It introduces a comprehensive phase diagram of excitonic states in trilayer heterostructures, highlighting the emergence of quadrupolar superfluidity and other novel phases due to dipolar correlations and charge tunneling effects.

Findings

Quadrupolar superfluid appears under strong dipole fluctuations.

Droplet states form when charge tunneling is suppressed.

Partially fragmented condensates occur at high exciton densities.

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 orientation fluctuates due to 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 competing quadrupolar and dipolar superfluid states. Furthermore, at a large exciton mass and high density, we find a staggered dipolar crystal. Our detailed study of the dependence of exciton energy shifts on an external electric field directly interprets existing experimental data and underscores the crucial role of the antiparallel dipolar configuration. Our results provide a guide for future experimental explorations of quantum phases of trilayer excitons.