Exciton density waves in Coulomb-coupled dual moir\'e lattices

TL;DR

This study demonstrates the formation of exciton density waves and correlated insulating states in Coulomb-coupled moiré lattices of layered TMD heterostructures, revealing new many-boson phenomena in solid-state systems.

Contribution

It introduces a solid-state platform of Coulomb-coupled moiré lattices supporting correlated excitonic states and density waves, advancing understanding of many-boson physics in 2D materials.

Findings

Observation of correlated insulating states at specific filling factors.

Identification of exciton density waves in a Bose-Fermi mixture.

Formation of generalized Wigner crystals restricting exciton fluid movement.

Abstract

Strongly correlated bosons in a lattice are a platform to realize rich bosonic states of matter and quantum phase transitions. While strongly correlated bosons in a lattice have been studied in cold-atom experiments, their realization in a solid-state system has remained challenging. Here we trap interlayer excitons--bosons composed of bound electron-hole pairs--in a lattice provided by an angle-aligned WS2/bilayer WSe2/WS2 multilayer; the heterostructure supports Coulomb-coupled triangular moir\'e lattices of nearly identical period at the top and bottom interfaces. We observe correlated insulating states when the combined electron filling factor of the two lattices, with arbitrary partitions, equals to 1/3,2/3,4/3 and 5/3. These new states can be interpreted as exciton density waves in a Bose-Fermi mixture of excitons and holes. Because of the strong repulsive interactions between the constituents, the holes form robust generalized Wigner crystals , which restrict the exciton fluid to channels that spontaneously break the translational symmetry of the lattice. Our results demonstrate that Coulomb-coupled moir\'e lattices are fertile ground for correlated many-boson phenomena.