Evidence for Exciton Crystals in a 2D Semiconductor Heterotrilayer

Abstract

Two-dimensional (2D) transition metal dichalcogenides (TMDC) and their moiré interfaces have been demonstrated for correlated electron states, including Mott insulators and electron/hole crystals commensurate with moiré superlattices. Here we present spectroscopic evidences for ordered bosons - interlayer exciton crystals in a WSe2/MoSe2/WSe2 trilayer, where the enhanced Coulomb interactions over those in heterobilayers have been predicted to result in exciton ordering. While the dipolar interlayer excitons in the heterobilayer may be ordered by the periodic moiré traps, their mutual repulsion results in de-trapping at exciton density n_ex larger than 10^11 cm^-2 to form mobile exciton gases and further to electron-hole plasmas, both accompanied by broadening in photoluminescence (PL) peaks and large increases in mobility. In contrast, ordered interlayer excitons in the trilayer are characterized by negligible mobility and by sharper PL peaks persisting to n_ex approximately 10^12 cm^-2. We present evidences for the predicted quadrupolar exciton crystal and its transitions to dipolar excitons either with increasing n_ex or by an applied electric field. These ordered interlayer excitons may serve as models for the exploration of quantum phase transitions and quantum coherent phenomena.

19 pages, 4 figures, SI

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Cited by in corpus (13)

• Quadrupolar Excitons and Hybridized Interlayer Mott Insulator in a Trilayer Moiré Superlattice
• Excitonic Mott insulator in a Bose-Fermi-Hubbard system of moiré ${\mathrm{WS}}_2$/${\mathrm{WSe}}_2$ heterobilayer
• Quadrupolar Excitons in MoSe${}_2$ Bilayers
• Quadrupolar and dipolar excitons in symmetric trilayer heterostructures: Insights from first principles theory
• Electrically controlled photonic circuits of field-induced dipolaritons with huge nonlinearities
• Dipolar interactions enhanced by two-dimensional dielectric screening in few-layer van der Waals structures
• Twistronics and moiré superlattice physics in 2D transition metal dichalcogenides
• Strong Correlation Driven Quadrupolar to Dipolar Exciton Transitions in a Trilayer Moiré Superlattice
• Long-range spatial extension of exciton states in van der Waals heterostructure
• Coulomb potential screening via charged carriers and charge-neutral dipoles/excitons in two-dimensional case
• Correlated phases of moat-band excitons in two dimensions
• Robust Interlayer Exciton Interplay in Twisted van der Waals Heterotrilayer on a Broadband Bragg Reflector up to Room Temperature
• Supermoiré-trapped quadrupolar exciton