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. At the heart of this realm lies the moiré flatband, a key player in shaping advanced light-matter interactions, such as laser emission and second harmonic generation. In moiré physics and its relevant applications, wielding control over flatbands is a pivotal superpower.
A New Path to Control Moiré Flatbands
Moiré flatbands are typically generated with special structures, often manipulated through a dance of rotation angles (magic angle) and spacings (magic distance) between the two lattice layers. However, a collaborative research team from the University of Electronic Science and Technology of China, Anqing Normal University, Guangxi University, and Nankai University has proposed a new way to control moiré flatbands. They have discovered that by adjusting the band offset of two photonic lattices in the parameter space, two robust groups of flatbands can arise within a broad range of band offset.
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 observed that the band offset effectively controls the moiré flatbands, including the appearance and disappearance of certain flatbands in the superlattice. They also found that certain flatbands stay steadily within a broad range of band offset.
The robustness of these flatbands challenges the conventional belief that obtaining nontrivial superlattices requires meticulous lattice control. The researchers have demonstrated that by altering structural parameters, the resonant frequencies of these flatbands can be adjusted. This breakthrough enables the creation of novel multiresonant moiré devices.
To understand the mechanism behind robust flatband formation, the authors of the study proposed a simple yet effective diagrammatic model based on the coupled-mode theory. This model takes into account the structural characteristics of the moiré superlattices and reveals the similarities and differences in the formation of these flatbands. The authors further incorporated full-wave calculations into the diagrammatic model, successfully predicting the field distribution of these robust flatbands.
The diagrammatic model not only serves as a tool but also offers a window into the world of flatband formation across diverse moiré superlattices. It uncovers previously uncharted paths in moiré physics, allowing researchers to explore innovative moiré devices and delve deeper into the captivating realm of moiré physics.
Unlocking the Potential of Moiré Flatbands
With the power to control and tune moiré flatband resonance frequencies through band offset adjustments, a realm of multi-resonant and high-quality moiré superlattices emerges. This breakthrough opens up new opportunities for advanced light-matter interactions, as well as the development of more efficient and versatile moiré devices.
The ability to manipulate moiré flatbands with relative ease and precision offers promising prospects in various fields, including photonics, optoelectronics, and quantum computing. The findings of this research not only contribute to the fundamental understanding of moiré physics but also pave the way for future technological advancements.
The discovery of a new method to control moiré flatbands by adjusting the band offset of photonic lattices in the parameter space unveils new possibilities in moiré photonics. This breakthrough allows for the creation of multiresonant moiré devices and offers insights into the formation and disappearance of flatbands. Harnessing the power of moiré flatbands opens up opportunities for advancements in advanced light-matter interactions and the exploration of the fascinating world of moiré physics.