Light–matter coupling in the terahertz (THz) regime is an important asset for future THz lasing, sensing, and quantum technologies, but it was previously realized in complex inorganic microcavities at cryogenic temperatures. Here we report on a simple organic meta-cavity formed with a patch-antenna array on an organic 4-N,N-dimethylamino-4′-N′-methyl-stilbazolium tosylate (DAST) single crystal, and particularly, the resultant observation of resonances and Rabi splitting in the THz regime. This is resulted from the coupling between two oscillators: a DAST optical phonon mode and the patch-antenna array meta-cavity. The birefringence of the DAST single crystal manifests itself in a polarization dependent response of the geometrically symmetric structure, with which the resonance of the cavity can be tuned close to that of DAST. A large Rabi splitting of 0.28 THz, corresponding to 25% of the DAST resonant absorption frequency, was experimentally measured at room temperature. Besides the incident polarization angle, the coupling can also be tuned by the operating temperature. This work presents the first experimental realization of room temperature coupling Rabi splitting in an organic single crystal at THz frequencies, opening up a promising organic avenue toward otherwise unattainable performance and inspiring the development of new organic THz devices.
The piezoelectric and elastic properties of a molecular piezoelectric meta-nitroaniline (mNA) in its singlecrystal form were investigated in the framework of first-principles density functional perturbation theory (DFPT). Results support the recent experimental findings those despite being soft and flexible, mNA's piezoelectric coefficients are an order of magnitude greater than that of ZnO and LiNbO 3 . A molecularlevel insight into the piezoelectric properties of mNA is provided. These results are helpful not only for better understanding mNA, but also for developing new piezoelectric materials.
Cross-lingual Entity Typing (CLET) aims at improving the quality of entity type prediction by transferring semantic knowledge learned from rich-resourced languages to low-resourced languages. In this paper, by utilizing multilingual transfer learning via the mixture-of-experts approach, our model dynamically capture the relationship between target language and each source language, and effectively generalize to predict types of unseen entities in new languages. Extensive experiments on multilingual datasets show that our method significantly outperforms multiple baselines and can robustly handle negative transfer. We questioned the relationship between language similarity and the performance of CLET. With a series of experiments, we refute the commonsense that the more source the better, and propose the Similarity Hypothesis for CLET.
Although vanadium oxides (VO x ) are important functional materials for academic research and industrial applications, the reaction mechanism of VO x prepared by organic sol–gel remains unclear. In order to investigate this mechanism, VO x organic sols were reacted at different temperatures, by which various VO x thin films were prepared. The products were systematically characterized by infrared spectroscopy, Raman spectroscopy, UV–vis spectroscopy, thermogravimetric analysis, scanning electron microscopy, x-ray diffraction, and a high resistance meter. Results reveal that vanadium alkoxides are created through an alcoholysis reaction of V2O5 powder and isobutyl alcohol, and then a condensation reaction of the vanadium alkoxides leads to the formation of VO x networks. The as-prepared sols are strongly temperature-dependent, causing different chemical structures and physical properties for the resulting VO x films. Particularly, a moderate temperature of 110 °C prompts both alcoholysis and condensation reactions, and thus the VO x films that are produced by the sol reacted at 110 °C possess a low resistivity of 23 Ω cm, a high temperature coefficient resistance (TCR) of −3.2% K−1, and a low average transmittance of 54% in 580–1100 nm, compared with those prepared by the sols reacted at lower or higher temperatures. Therefore, 110 °C is a desirable sol temperature for producing VO x films serving as high-quality bolometric materials for uncooled infrared detectors. This work discloses not only the reaction mechanism of VO x films prepared by organic sol–gel, but also the route to yield desirable VO x films for optoelectronic applications.
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