Boosting Exciton Transport in WSe₂ by Engineering Its Photonic Substrate

Abstract

Efficient transport of exciton in 2D semiconductors is of great importance for developing high-speed optoelectronic devices. However, excitons in layered transition-metal dichalcogenides, a class of 2D semiconductors, can only transport over a few hundred nanometers, due to the multiple collision with phonons and disorders. Here, we boost the transport capability of excitons in layered tungsten disulfide (WSe2) by engineering its photonic environment. Extended polaritonic states are formed between the flying interfacial photons and the tightly bounded excitons, with the Rabi splitting scaling with the square root of the layer number of WSe2. The light-mass polariton can travel several or even tens of micrometers, with its lifetime down to a femtosecond scale. Therefore, these results provide a unique route for designing high-speed polaritonic devices based on 2D semiconductors.

Long-Range Propagation of Exciton-Polaritons in Large-Area 2D Semiconductor Monolayers

“…For each system, we observe that the lower-energy (longerwavelength) polariton propagates over a longer distance as the BSW fraction of polariton states is increased due to increased detuning of the polariton mode from the exciton absorption spectrum. 29,30 This makes BSWP systems promising for energy transport, which differs from waveguiding luminescent solar concentrators that are limited by reabsorption of the guided light. 36,37 Moreover, centimeter-sized WS 2 monolayers used in BSWP structures allow us to study the propagation properties with excitation at different spots in the same device.…”

“…Recently, a monolayer TMD-based BSW polariton (BSWP) has been demonstrated to yield propagation lengths of several tens of micrometers based on mechanically exfoliated TMDs with a lateral size of only a few square micrometers. 29,30 Such a small scale presents substantial challenges for practical on-chip TMD-based devices. 31,32 Also, there remains a need to systematically engineer long-range BSWP propagation in TMD monolayers.…”

“…Recently, a monolayer TMD-based BSW polariton (BSWP) has been demonstrated to yield propagation lengths of several tens of micrometers based on mechanically exfoliated TMDs with a lateral size of only a few square micrometers. , Such a small scale presents substantial challenges for practical on-chip TMD-based devices. , Also, there remains a need to systematically engineer long-range BSWP propagation in TMD monolayers. In contrast to previous work using micrometer-scale TMD flakes, , here we employ centimeter-scale, metal–organic chemical vapor deposition (MOCVD)-grown monolayers for the BSW-exciton strong coupling and demonstrate BSWP-mediated long-range energy transport at room temperature. Importantly, the long-range BSWP propagation studied at different excitation spots across the thin film demonstrates the quality of centimeter-scale TMD monolayers for energy transport, which makes systems with large-size TMDs far more practical for device applications than those comprising micron-scale flakes.…”

“…Recently, a monolayer TMD-based BSW polariton (BSWP) has been demonstrated to yield propagation lengths of several tens of micrometers based on mechanically exfoliated TMDs with a lateral size of only a few square micrometers. , Such a small scale presents substantial challenges for practical on-chip TMD-based devices. , Also, there remains a need to systematically engineer long-range BSWP propagation in TMD monolayers. In contrast to previous work using micrometer-scale TMD flakes, , here we employ centimeter-scale, metal–organic chemical vapor deposition (MOCVD)-grown monolayers for the BSW-exciton strong coupling and demonstrate BSWP-mediated long-range energy transport at room temperature.…”

Theoretical Analysis of Exciton Wave Packet Dynamics in Polaritonic Wires

“…Interaction between light and matter is enhanced within optical microcavities and plasmonic devices due to the confinement of the electromagnetic (EM) field to a small region of space . These structures have been used to design landscapes where the strong light–matter coupling regime achieved enables the emergence of light–matter hybrid states commonly denoted (cavity) polaritons. , The presence of these polaritonic states has been shown to modify energy transport, − conductivity and photoconductivity, − optical response, , and chemical reactions. ,− Hence, these devices have been not only objects of theoretical interest but also prospectus of new technology. ,, …”