When two lattices with distinct angles or periodicities come together, they conjure a moiré superlattice—a realm where astonishing phenomena like superconductivity and optical solitons spring to life. In this realm, the moiré flatband plays a crucial role in shaping advanced light-matter interactions. The ability to control flatbands is a pivotal superpower in moiré physics and its applications.
A research team from the University of Electronic Science and Technology of China, Anqing Normal University, Guangxi University, and Nankai University recently proposed a new method for controlling moiré flatbands. Instead of manipulating rotation angles and spacings between lattice layers, the team focused on adjusting the band offset of two photonic lattices in the parameter space.
The team made a groundbreaking discovery during their study. By varying the band offset through changing the thickness of one layer of the superlattices, they observed the appearance and disappearance of different flatbands in the superlattice. Interestingly, they also found the existence of two robust groups of flatbands within a broad range of band offset. These steady flatbands provide opportunities for precise control of structural parameters and the creation of novel multiresonant moiré devices.
The resonant frequencies of the robust flatbands can be adjusted by altering structural parameters. This capability enables the development of high-quality doubly resonant moiré superlattices. The researchers demonstrated the feasibility of these moiré superlattices through systematic investigations of localized modes originating from the two groups of flatbands. Thus, the control of moiré flatband resonance frequencies through band offset adjustments becomes a powerful tool for crafting extraordinary moiré superlattices.
To elucidate the mechanism behind robust flatband formation, the research team proposed a simple yet effective diagrammatic model based on the coupled-mode theory. This model takes into account the structural characteristics of moiré superlattices and reveals similarities and differences in the formation of these flatbands. By incorporating full-wave calculations into the diagrammatic model, the researchers successfully predicted the field distribution of the robust flatbands, further confirming their findings.
Controlling moiré flatbands by adjusting the band offset in parameter space offers an elegantly simple method to unlock nontrivial superlattices. This breakthrough holds the key to unraveling the mysteries of flatband emergence and disappearance. The ability to command the frequencies of these flatbands gives rise to a realm of multiresonant and high-quality moiré superlattices.
The diagrammatic model developed by the research team is not solely a tool but a window into the world of flatband formation across diverse moiré superlattices. It provides insights that can inspire future explorations into innovative moiré devices and the captivating realm of moiré physics.
The research on controlling moiré flatbands by adjusting the band offset brings forth new opportunities in photonics. By understanding and manipulating the resonance frequencies of these flatbands, researchers can create high-quality moiré superlattices with multiple resonances. The discovery of robust flatbands within a broad range of band offset opens doors to precise control of structural parameters and the development of novel moiré devices. The diagrammatic model serves as a valuable tool and a source of inspiration for further investigations into the intriguing field of moiré physics.
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