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interests The authors declare that they have no competing interests. Authors’ contributions ZPL planned and performed the experiments, collected and analyzed the data, and wrote the paper. KBT supervised the project, analyzed the results, and wrote the paper. QYH and LLW helped with the synthesis of the AL3818 materials and the collection of the data. RT did the Rietveld fit of the obtained polytypic nanoplates. All the authors discussed the results and commented on the manuscript. All authors read and approved the final manuscript.”
“Background Metamaterials (MMs) Temozolomide concentration are artificially engineered composites that attract considerable interests due to their exceptional electromagnetic properties, which are not typically found in nature, such as negative refractive index and cloaking [1–4]. These MMs with various subwavelength resonant elements have offered magnetic and/or electric resonant eFT508 concentration responses to incident electromagnetic radiation, scalable from the microwave frequencies up to the terahertz and optical ones [5–7]. Particularly, nanohole resonators embedded in metal-dielectric-metal (MDM) multilayers are frequently used as building blocks of negative-refractive-index MMs [8–11], owing to

the coupling between surface plasmons counterpropagating on the two closely spaced interfaces which results in a closed loop of the electric currents. This gives rise to magnetic dipolar resonances between the two coupled metal layers, while the continuous

metallic strip parts provide the electric resonance moments [12, 13]. All these features make the nanohole array perforating through MDM films become a strong candidate for developing three-dimensional negative-index MMs [14, 15]. One of the obstacles in this progress is the resonance responses of MMs to the impinge light Cediranib (AZD2171) which are usually fixed once the dimension of the structure is determined, thus making the MMs possess a limited bandwidth. However, for many applications (switching, modulation, filtering, etc.), it would be highly desirable to tune the MM resonances over a wide bandwidth. To this end, tunable photonic MMs, the spectral range of which can be controlled by changing the dielectric environment of the resonator with liquid crystals (LCs) [16–18]; phase transition materials [19, 20]; and optical pumping [21, 22] have been discussed recently. However, the challenge is to develop tunable MDM-MMs in the near-infrared (NIR) regime. It is due to the fact that frequency tunability of the MDM-MM mainly requires for the interlayer dielectric material to possess a tunable effective dielectric constant in the NIR region, hence limiting the choice of the active materials. Here, we take a different approach to actively tune the resonant frequency of the MDM-MMs in the NIR regions by using bismuth selenide (Bi2Se3) as the dielectric layer. Recently, a rising Dirac material – topological insulators (TIs) – had been intensively researched in condensed matter physics [23, 24].