Moiré superlattices have always fascinated scientists due to the astonishing phenomena that can arise when two lattices with distinct angles or periodicities come together. These phenomena include superconductivity and optical solitons, which have significant implications in various fields. At the core of these phenomena lies the moiré flatband, a crucial element in shaping advanced light-matter interactions, such as laser emission and second harmonic generation. The ability to control flatbands is seen as a pivotal superpower in moiré physics and its applications. Traditionally, moiré flatbands are generated using special structures and manipulating rotation angles and spacings between the two lattice layers. However, a collaborative research team has proposed a groundbreaking method to control moiré flatbands by adjusting the band offset of two photonic lattices in the parameter space.
The team, consisting of researchers from the University of Electronic Science and Technology of China, Anqing Normal University, Guangxi University, and Nankai University, discovered that by varying the band offset, two robust groups of flatbands can emerge within a broad range of band offset. These flatbands maintain their existence steadily, alleviating the need for strict control over structural parameters. This breakthrough opens up new possibilities in moiré photonics, allowing for the creation of novel multiresonant moiré devices by adjusting the resonant frequencies of these robust flatbands through structural parameter alterations.
To achieve this breakthrough, the researchers started with a mismatched silicon-based bilayer moiré superlattice and adjusted the band offset by varying the thickness of one layer of the superlattices. By calculating the superlattice band structure at different band offsets, they discovered that the band offset effectively controls the moiré flatbands, including the appearance and disappearance of some flatbands in the superlattice. Simultaneously, they found that certain flatbands remain consistently within a wide range of band offset. The robustness of these flatbands reveals a surprising secret: crafting extraordinary moiré superlattices doesn’t require meticulous lattice control but allows for the tuning of moiré flatband resonance frequencies through band offset adjustments.
To elucidate the mechanism behind the formation of robust flatbands, the authors proposed a simple yet effective diagrammatic model based on the coupled-mode theory, considering the structural characteristics of the moiré superlattices. This model revealed both the similarities and differences in the formation of these flatbands. To confirm their findings, the authors incorporated full-wave calculations into the diagrammatic model, successfully predicting the field distribution of these robust flatbands. This advance opens up new horizons in moiré physics, where controlling moiré flatbands through band offset adjustments in the parameter space becomes an elegantly simple method to unlock nontrivial superlattices and unravel the mysteries of flatband emergence and disappearance.
Exploring the Implications
With the ability to control the frequencies of these flatbands, a whole new realm of multi-resonant and high-quality moiré superlattices emerges. This paves the way for innovative moiré devices with various applications. Furthermore, the diagrammatic model developed by the researchers acts as more than just a tool—it provides a window into the world of flatband formation across diverse moiré superlattices. This research has the potential to inspire future explorations into the captivating realm of moiré physics and stimulate the development of new and exciting moiré devices.
The discovery of robust flatbands within a broad range of band offset in moiré superlattices marks a significant advancement in the field of moiré physics. The ability to control these flatbands through band offset adjustments offers a simple yet effective method to achieve nontrivial superlattices and explore the mysteries of flatband formation. This breakthrough opens up new opportunities for the creation of novel moiré devices and sheds light on the intricate world of moiré physics. With continued research and exploration, the power of robust flatbands in moiré superlattices can revolutionize various fields and lead to exciting technological advancements.
Leave a Reply