Cavity-control of interlayer excitons in van der Waals heterostructures

Abstract

Monolayer transition metal dichalcogenides integrated in optical microcavities host exciton-polaritons as a hallmark of the strong light-matter coupling regime. Analogous concepts for hybrid light-matter systems employing spatially indirect excitons with a permanent electric dipole moment in heterobilayer crystals promise realizations of exciton-polariton gases and condensates with inherent dipolar interactions. Here, we implement cavity-control of interlayer excitons in vertical MoSe 2 -WSe 2 heterostructures. Our experiments demonstrate the Purcell effect for heterobilayer emission in cavity-modified photonic environments, and quantify the light-matter coupling strength of interlayer excitons. The results will facilitate further developments of dipolar exciton-polariton gases and condensates in hybrid cavity – van der Waals heterostructure systems.

Moiré excitons in MoSe2-WSe2 heterobilayers and heterotrilayers

“…Despite numerous experimental and theoretical studies of MoSe 2 -WSe 2 HBLs, the origin of the lowestenergy PL remains a subject of debate 22 . While the majority of experimental studies interpret the HBL emission in terms of zeromomentum interlayer excitons with K or K 0 valley electrons and holes in MoSe 2 and WSe 2 15,16,19,21,[23][24][25][26][27][28][29] , others invoke excitons built from hybridized HBL conduction band states at Q pockets [30][31][32] , located roughly halfway between the center of the first Brillouin zone at Γ and K or K 0 valleys. Band structure calculations indeed suggest that hybridization of states near Q conduction band and Γ valence band of MoSe 2 and WSe 2 gives rise to strong energy renormalization upon HBL formation 2,33,34 which might turn either QK or QΓ interlayer excitons, composed of electrons at Q and holes at K or Γ, into the lowest-energy states.…”

Polariton panorama

“…Experiments on metallic nanoparticles show that charge transmitted between the pair of nanoparticles through a conducting pathway leads to a characteristic plasmonic response [69] termed charge transfer plasmons. Interlayer exciton in transition metal dichalcogenide (TMDC) heterostructures (e.g., MoSe 2 /WSe 2 ) also involves charge transfer from one layer to another; the relevant microcavity polaritons [70] are classified as charge transfer exciton polaritons.…”

Spontaneous Emission of Plasmon‐Exciton Polaritons Revealed by Ultrafast Nonradiative Decays

“…[2] Stronger PL intensity corresponds to a larger emission rate and a shorter radiative lifetime. [27] To directly characterize the change of PL intensity, PL EF is introduced. [40][41][42]48] In this work, it is defined by dividing the luminescence intensity of LP (i.e., with nanodisks) to A exciton in pristine WSe 2 monolayer at the same flake, as shown in Figure 1c In region I, a gradual increase of emission intensity is observed.…”

“…[22][23][24][25] The enhanced emission brightness under weak coupling can be explained by the Purcell effect. [26,27] However, the luminescence nature of exciton-polaritons is thoroughly modified. [28] For example, the photoluminescence (PL) peak can split into a doublet, [29] and the photonlike mode has stronger luminescence than the excitonlike mode.…”