We determine the zero temeperature phase diagram of excitons in the symmetric transition-metal dichalcogenide tri-layer heterosctructure WSe2/MoSe2/WSe2. First principle calculations reveal two distinct types of interlayer excitonic states, a lower energy symmetric quadrupole and a higher energy asymmetric dipole. While interaction between quadrupolar excitons is always repulsive, anti-parallel dipolar excitons attract at large distances. We find quantum phase transitions between a repulsive quadrupole lattice phase and a staggered (anti-parallel) dipolar lattice phase, driven by the competition between the exciton-exciton interactions and the single exciton energies. Remarkably, the intrinsic nature of each interlayer exciton is completely different in each phase. This is a striking example for the possible rich quantum physics in a system where the single particle properties and the many-body state are dynamically coupled through the particle interactions.
@article{arxiv.2004.06687,
title = {Quantum phase transitions of tri-layer excitons in atomically thin heterostructures},
author = {Yevgeny Slobodkin and Yotam Mazuz-Harpaz and Sivan Refaely-Abramson and Snir Gazit and Hadar Steinberg and Ronen Rapaport},
journal= {arXiv preprint arXiv:2004.06687},
year = {2020}
}