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Transport of elementary excitations is a fundamental property of two-dimensional (2D) semiconductors, essential for wide-ranging phenomena and device applications. Although exciton transport reported in 2D materials barely exceeds 1 to 2 micrometers, coherent coupling of excitons with photons to form polaritons enables extended transport lengths and offers opportunities to use photonic mode engineering for tailored transport. Conventional vertical cavity or waveguide polaritons, however, are challenging to tune and integrate into photonic circuits. We report the transport of transition metal dichalcogenide polaritons in 2D photonic crystals that are highly versatile for tuning, mode engineering, and integration. We achieve an order-of-magnitude enhancement in transport length compared to bare excitons and reveal transport dependence on polariton dispersion and population dynamics, which are controlled via photonic crystal design and pump intensity. Stimulated relaxation observed in the system suggests the potential for forming superfluid polaritons with frictionless transport. These findings establish 2D photonic crystal polaritons as a versatile platform for advancing photonic energy transport technologies. 

Since the discovery of two-dimensional transition metal dichalcogenide monolayers as direct bandgap semiconductors with pronounced room-temperature exciton transitions, research on excitons and polaritons in these materials has exploded worldwide. Here, we give an introductory tutorial on the basic properties of excitons and polaritons in these materials, emphasizing how they are different from those in conventional semiconductors, and discuss some of the most exciting new phenomena reported. 

Vibrational and electronic strong coupling of light with molecular excitations has shown promise for modifying chemical reaction rates. However, the Tavis–Cummings model often used to model such polaritonic chemistry considers only a single discrete cavity mode coupled with the molecular modes, while experimental systems generally consist of a larger number of molecules in cavities with a continuum of modes. Here, we model the polaritonic effects of multimode cavities of arbitrary dimensions and filled with a large number of molecules. We obtain the dependence of the effects on the dimensionality of the cavity, the molecular oscillator strength, and molecular concentration. Combining our model with the transition state theory, we show that polaritonic effects can be altered by a few orders of magnitude compared to including only a single cavity mode, and that the effect is stronger with a larger molecular dipole moment and molecular concentration. However, the change remains negligibly small for realistic chemical systems due to the large number of dark states. 

Abstract There is no consensus yet on whether the precursor and the main burst of gamma-ray bursts (GRBs) have the same origin, and their jet composition is still unclear. In order to further investigate this issue, we systematically search 21 Fermi GRBs with both a precursor and main burst for spectral analysis. We first perform Bayesian time-resolved spectral analysis and find that almost all the precursors and the main bursts (94.4%) exhibit thermal components and that the vast majority of them have a low-energy spectral index (α; 72.2%) that exceeds the limit of synchrotron radiation. We then analyze the evolution and correlation of the spectral parameters and find that approximately half of theα(50%) of the precursors and the main bursts evolve in a similar pattern, while peak energy (E_p; 55.6%) behaves similarly, and their evolution is mainly characterized by flux tracking; for theα−F(the flux) relation, more than half of the precursors and the main bursts (61.1%) exhibit roughly similar patterns; theE_p−Frelation in both the precursor and main burst (100%) exhibits a positive correlation of at least moderate strength. Next, we constrain the outflow properties of the precursors and the main bursts and find that most of them exhibit typical properties of photosphere radiation. Finally, we compare the time-integrated spectra of the precursors and the main bursts and find that nearly all of them are located in similar regions of the Amati relation and follow the Yonetoku relation. Therefore, we conclude that main bursts are continuations of precursors and may share a common physical origin. 

Electrically controlled photonic circuits hold promise for information technologies with greatly improved energy efficiency and quantum information processing capabilities. However, weak nonlinearity and electrical response of typical photonic materials have been two critical challenges. Therefore, hybrid electronic-photonic systems, such as semiconductor exciton polaritons, have been intensely investigated for their potential to allow higher nonlinearity and electrical control, with limited success so far. Here we demonstrate an electrically gated waveguide architecture for field induced dipolar polaritons that allows enhanced and electrically controllable polariton nonlinearities, enabling an electrically tuned reflecting switch (mirror) and transistor of the dipolar polaritons. The polariton transistor displays blockade and antiblockade by compressing a dilute dipolar-polariton pulse exhibiting very strong dipolar interactions. The large nonlinearities are explained using a simple density-dependent dipolar polarization field that very effectively screens the external electric field. We project that a quantum blockade at the single polariton level is feasible in such a device. Published by the American Physical Society2024 

Abstract The unique optical properties of transition metal dichalcogenide (TMD) monolayers have attracted significant attention for both photonics applications and fundamental studies of low-dimensional systems. TMD monolayers of high optical quality, however, have been limited to micron-sized flakes produced by low-throughput and labour-intensive processes, whereas large-area films are often affected by surface defects and large inhomogeneity. Here we report a rapid and reliable method to synthesize macroscopic-scale TMD monolayers of uniform, high optical quality. Using 1-dodecanol encapsulation combined with gold-tape-assisted exfoliation, we obtain monolayers with lateral size > 1 mm, exhibiting exciton energy, linewidth, and quantum yield uniform over the whole area and close to those of high-quality micron-sized flakes. We tentatively associate the role of the two molecular encapsulating layers as isolating the TMD from the substrate and passivating the chalcogen vacancies, respectively. We demonstrate the utility of our encapsulated monolayers by scalable integration with an array of photonic crystal cavities, creating polariton arrays with enhanced light-matter coupling strength. This work provides a pathway to achieving high-quality two-dimensional materials over large areas, enabling research and technology development beyond individual micron-sized devices.