Unlocking New Possibilities: Controlling Moiré Flatbands Through Band Offset Adjustments

The realm of moiré physics is a captivating field where distinct lattices intersect, giving rise to extraordinary phenomena such as superconductivity and optical solitons. At the heart of this realm lies the moiré flatband, a crucial element that shapes advanced light-matter interactions. Wielding control over flatbands is a pivotal superpower in moiré physics and its applications. Traditionally, moiré flatbands are generated through special structures and manipulation of rotation angles and spacings between lattice layers. However, a collaborative research team from various universities in China has recently proposed an innovative method to control moiré flatbands by adjusting the band offset of two photonic lattices in the parameter space.

The team’s study, as reported in Advanced Photonics Nexus, showcases their discovery of robust groups of flatbands that emerge within a broad range of band offset. These flatbands maintain their existence even as the band offset changes, providing a more flexible approach to obtaining nontrivial superlattices. The researchers achieved this breakthrough by altering the band offset through the thickness variation of one layer in a mismatched silicon-based bilayer moiré superlattice.

By manipulating the structural parameters, the research team could adjust the resonant frequencies of these robust flatbands. This ability opens up new possibilities for creating novel multiresonant moiré devices. The resonant frequencies of flatbands can be tailored to specific requirements by precisely controlling the band offset. As a testament to this power, the researchers investigated the localized modes originating from the robust flatbands in moiré superlattices, confirming the feasibility of high-quality doubly resonant moiré superlattices.

To understand the mechanism behind the formation of these robust flatbands, the authors proposed a simple yet effective diagrammatic model based on the coupled-mode theory. The model takes into account the structural characteristics of the moiré superlattices and reveals the similarities and differences in the formation of flatbands. Full-wave calculations were also incorporated into the diagrammatic model to predict the field distribution of these flatbands, providing further confirmation of the model’s effectiveness.

The ability to control moiré flatbands through band offset adjustments opens new horizons in moiré physics. This elegant and simple method holds the key to unlocking nontrivial superlattices and unraveling the mysteries surrounding flatband emergence and disappearance. With precise control over the frequencies of these flatbands, a realm of multi-resonant and high-quality moiré superlattices emerges. Furthermore, the diagrammatic model serves as a window into the world of flatband formation across diverse moiré superlattices. It not only acts as a tool but also inspires future explorations into innovative moiré devices and the captivating realm of moiré physics.

The ability to control moiré flatbands by tuning the band offset in parameter space is a significant advancement in moiré physics. This research paves the way for the development of new moiré devices with enhanced functionalities and provides insights into the underlying principles of flatband formation. The implications of this breakthrough extend beyond moiré physics, as the newfound control over flatbands has the potential to revolutionize fields such as laser emission and second harmonic generation. As we continue to delve into the mysteries of moiré physics, the doors to unprecedented opportunities for innovation and discovery are wide open.


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